yes i have a bored tb and the kegger will support the cfm im running with the new heads. as far as tuning goes...im running a custom flash my caplin speed.

funny thing is...its not chopped...im talking about the complete system welded with the tips at the rear bumper...just a really bad drone.

im obd1...i dont have a downstream.

lol...thats not my exhaust picture...i just copied and pasted that pic so the OP could see it easier.

i didnt use nonfoulers...i cut the original bung out of the cat and welded it to my y-pipe. the bulb is in the exhaust stream.

 

Oh, that's right, you have FM 50's, don't you? I keep forgetting since that. I thought you were chopped.

I hate to tell ya this, but every FM 50's I've ever installed and heard droned really bad. They've got a nice idle and top end sound, but that 2000K sweet spot when you are highway driving makes the worst sound possible. Be glad you don't have a 5.3 with MDS. Now that's a droning sumbitch.

At this point, I'd say plug a new O2 sensor in. Those sensors are fragile and can be a bit fussy.

 

i think thats what im gonna do.

the fm50 sounded pretty good with no drone when the cat was there...but dang...replace the cat and it all goes down hill. first chance i get i am gonna replace the entire exhaust. headers back...im doing duals with 2" pipe thru to turndowns in front of the rear axle...i just havent decided on mufflers.

i just want the best flow possible with a good temperature and a low rumble...thats it.

 

Where is the egr valve located? Crankshaft sensor?

 

uhhhh... egr valve is in the muffler and the crankshaft sensor is in the catalytic converter. j/k

egr is in paseenger side exhaust manifold. im guessing you are talking about the crankshaft position sensor...hard to explain...hard to reach...lol.

 

first i have a 1999 durango 4x4 5.9 3.92 gear that i took the cat off and just put a piece of pipe in its place because the cat got red hot because it was plunged all the o2 sensors are put in the pipe,now my ? is i thought the downstream senser was there to see it the cat is working or burning the exes fuel?
but the wrango runs great getting 14mpg consistent which is what it got with the cat before it got plunged so im confused?
I just used the piece of pipe for a temp fix and i was going to save up to buy the cat but im seeing there no need to buy it(also i dont have e-check)

i was also thinking of running true duels 2.25 inch with out cats through flowmaster 40s and ill just weld the bungs in and re install the sensers i guess unless you guys dont think this will work on my 2001 dodge 1500 4x4 5.9

 

I think it's the heads costing you the gas and the lack of cat making your head throb.

The heads let more air through, that requires more fuel to keep the a/f ratio the same. I remember you saying that you had significantly increased the CFM of the heads, so now you're "paying for it" in lower gas mileage. It could also be your tune.

I'd jump on the dyno and instead of tuning WOT, ask your buddy to check the idle and cruising fuel curves and adjust from there. I believe those are separate parameters than WOT fuel curves and could be adjusted to help your mileage. You could also contact B&G Chrysler as they are about the only ones that tune OBD-I.

If you replaced the cat with a straight pipe, you probably now have a length of pipe suitable to create a resonance or "drone" in the exhaust system. The expansion of the gas chamber at the cat not only lets more exhaust thru a more confined space, it also destroys the drone by changing the size of the pipe and consequentially the frequency needed to create a drone.

I'd try a hi flow cat or possibly a resonator in place of the cat. That should break up the drone.


EDIT: I just saw that picture of your Y pipe. Is that O2 sensor on the bottom of the pipe or the top? If that's the bottom, you have probably destroyed your O2 sensor. Condensation in the pipe will destroy an O2 sensor quickly if it's mounted under the 9 or 3 O'Clock positions on a pipe.