I have a 99 not 4 wheel drive that I tow with. I did the stainles steel mandrel bent cat back with a magnaflow which gave me a little extra notalot. I had 3.55 gears and went to 4.10 made a huge difference on hills. Used the Hypertech on 87 octane setting (can't even get 93 octane in CA). My reason was because the truck had the dreaded death flash. The reprogramming woke it up better than anything else. But I only attribute that to undoing the death flash. I have owned the truck since it was new and my first reaction was that it was back like it was originally. Put on a reworked 50 mm throttle body, not theFastman, but similar and nicely done. That seemed to give me better throttle response. I believe the reasoning for not going with the 52 is that it gives you more high end versus low end torgue, which is generally what you want for towing. At this point I am still debating on the CAI and whether it is really worth it. I do run a trueflow drop in filter.

 

Your most cost effective mods will be to the exhaust system.
Go with
1.dual catalytic converters (just use 2 and don't trust that a 'high flow' cat con really will be hig flowing)
2. Use a large muffler with 3 or 4 inch inlets and outlets
3. larger diameter Y pipes from engine to cats

A good exhaust system will have less than 3 psi of backpressure at full throttle and 4000 rpm, and will gain you 10-15 ft-lbs of torque in the important 1500-2500 rpm range where most towing is done.

If you want to add headers to the above exhaust system, be warned that the cost is high ($400-900 installed). The power and torque gains at 4000 rpm are small (typically 2-3% which for 245 hp would be about 7 hp at 4000 rpm), but the torque gain in the important 1500-2500 rpm will be only 1 or 2)
Don't be surprised after installing headers that you will have to fix exhaust leaks more than one time.

The ported throttle body will give about 2-3% gain at 4000 rpm, but very little gain 1500-2500 rpm. No MPG gain.

The cold air intake will be noisy & painted in a flashy color scheme, but will give almost no hp or torque gain.
See this link for proof found by 'independent' volunteers just like you:
http://www.lxforums.com/board/showthread.php?t=14140

In a careful test the MPG chance after installing a CAI will be zero, but if you only check the next tank of gas you always have a 50/50 chance that the MPG will bounce up or down (this is natural). Half the people who install CAI's truthfully report that they think their MPG went up, but it is just the way they did their testing.

The 180 thermostat will provide almost no hp or torque gain. MPG will go down very slightly, perhaps 0.2 MPG. Bore walls will wear faster at 180 than at 195 due to condensed acidic liquids that stay gases at higher coolant temperatures.

A true aftermarket PCM computer to control your engine and ignore pollution controls would give hp, torque and MPG gains but the cost is high: $1500-2000 installed unless you do it yourself with a Megasquirt system. The gains could be as high as 15-20%

Don't over look the effect tires will have on your tow vehicle and trailer, both on stopping distance and MPG. Low rolling resistance tires can easily improve your MPG 1-2.

Short stopping distance tires can save your life or property.

When day dreaming about towing performance, don't picture in your mind about how you are going to roar up steep hills at 79 mph.

Picture instead: What am I going to do if some dit-brain talking on her cell phone cuts in front of me without checking her mirror and causes me to have to panic stop with heavy trailer behind me. What am I going to do if this happens on a steep downhill?

 

I installed a 180 stat and my truck runs cooler.[sm=smiley24.gif] I can't say I noticed any gains in MPG or more power but it does run noticeably cooler.

 

Thanks everyone for all of the input. I had actually thought about the brake system as well. Specifically, how much would it cost to upgrade the brakes to larger discs in front and swap out the rear drums for discs. I hate having the rear drums back there. My trailer has surge brakes, but even so, ashort stop while towing the boat is not fun, and a true emergency stomp-on-the-brakes stop is a frightening prospect. I haven't checked the cost of the brakes upgrade, but I imagine it's not cheap.

So I think I've narrowed it down to these things:

Exhaust Mods (headers and new high-flow muffler or maybe complete cat-back). Will look into the cat converters as well.
ECU
1.7 rockers (maybe roller)
50mm tb (maybe)
Brakes (front upgrade and rear conversion -- if it doesn't cost waaayyyy too much).
Double check the gears... if it's 3.92, then I definitely won't touch it.

Of course, I've still got another month to think about these things, so who knows, I could end up doing more or maybe nothing at all.
What I'd really like to do is just buy a crate motor... if only I had 15k laying around -- but then, if I had that money I'd probably but putting a blower on the boat as well. Oh well, one can dream...

 

edited

 

How can I delete a post?

 

You can't ... you can ask a moderator to do it for you or just edit it down to nothing ... like you did.

 

Replacing the stock rocker arms with 1.7 roller rockers (Harlan Sharp are excellent) is basically a poor mans camshaft upgrade. You will get more lift and will notice more power. ($375 at Summit Racing) Might wish to replace your push rods at the same time as it's always a good thing to do when replacing rocker arms (about $90). You can also replace your roller lifters for an additional ($130).

With our MPI fuel injection, you only have 2 choices of intake manifolds. The stock barrel and the M1. The M1 causes a loss of low end torque while providing more HP on the high end. Not what you want for towing. You can do the mod to the barrel intake where you cut the runners down some. If your intake has the large center divider, also cut it down. If you do this make the new runner ends look like they did before you did the work. (tapered). ($ Gasket set, grinders, and elbow grease)

I also spoke with Dan Arkand about the 50 vs 52 mm throttle body and he advised me to go with the 50 as I need the lower end torque for towing. Can't remember the exact reason, but it was good enough to cause me to purchase the 50 over the 52. ($250 ?)

I installed the shorty ceramic edelbrock headers and am very pleased with the performance. They are direct fit so no additional exhaust work is required. ($370 @ Summit Racing)

One last thing I would recommend is the Mypertech PP III, power programmer. it woke up my engine even more. ($359 @ Summit Racing)

Good luck.

 

This doesn't seem to have been suggested yet. I saw significant imporovements when I installed a MSD 6A ignition box, MSD 8mm wires, and a MSD Baster SS coil. Then of course new plugs. If you do all of that you will be burning your fuel a lot better

I second the motion on the new throttle body. I ran a 50mm CNCed one for a couple years, it's on eBay right now btw:
http://cgi.ebay.com/ebaymotors/ws/eB...m=230112624776
The throttle body gave me a lot more low end torque. My engine pushed extremely hard from 2500-3000rpms which is just perfect for the 3.73 differential with over drive off (I have the same setup as you). I pull a large horse trailer with a GVWR higher than what my truck is rated at and going up hill my engine roars when I hold it in gear. With a manual even better improvements will be seen. I just upgraded (not sure yet if it's an upgrade) to a 52mm TB which was put on the early 5.9L Magnums that was in the 3rd Gen Body trucks before the Hemi. It comes from the factor CNCed:
http://cgi.ebay.com/ebaymotors/ws/eB...m=120083351782
The guy in the auction lied and said it was a "prototype", but now I've seen them around a lot, so I know it was just a late production change.

Anyway, Do the MSD thing! It was only $200-250 depending on how good of a deal you get.

 

Forgot to mention the MSD ignition setup. Mine is still in the box waiting for it to warm up here in Minnesnowta. I should have the MSD 6A and Blaster coil installed within the next week or so.