i have been running mine of performance with 93 octane. bone stock 11.5, 33x12.50 10.5, 33x12.50 plus [erformance tune 12.2. i can't complain!!!

 

But have you updated?

 

Like pcfixerpro said, have you updated recently though?

Timeline (approximates):
March 31: Switched the stock intake and plenum gasket with a modified intake ("kegger mod") and Hughes plenum kit. The truck had the Performance tune on it before the swap, didn't touch the tuner again until April 6.
April 6: Plugged tuner into PC, Superchips program reports an update and updates the tuner. I go out, plug the tuner in, program for 91 Performance tune. Everything is hunky dory, disconnect tuner, turn key... and severe stumbling and hesitation when you give it anymore than 5-10% throttle, almost like misfires. If you floor it (WOT), it will hestiate, stumble, hestitate, then you hear it pinging for a second, then stumble, hestiate. I immediately log onto the Superchips forums and initiate a discussion with their customer service about this.
April 7: Superchips CS forwards the issue onto the engineers, but tells me I am the only one to report this issue.
April 15: Engineers report back, files are good, no one else reported the issue, so it must be something wrong with my truck, and not the tuner.

Things I've done so far that did not solve the problem:
-Replaced pre-cat O2 sensor
-Replaced Autolite 3923 plugs (less than 5000 miles on them) with stock heat range NGK V-power plugs
-Replaced NGK V-power plugs with brand new Autolite 3923s
-Replaced MSD Blaster 2 coil with stock coil
-Made sure plug wires are routed properly

Here's a kicker...

After routing the wires per the TSB (which supposedly doesn't apply to 2001s anyway), it seemed to come out of it. Drove fine until I got on the highway, but even then the only issue was pinging at WOT at speeds above 60. I was down to 3/8 of a tank, so I drove it to my gas station for fuel. Filled her up, then started it. The hestitation, stumbling was back same as it had been before.

Only thing I can think of is that while I was routing the two wires that the TSB has you move, I may have bumped one of the sensors or sensor wiring harnesses. That may have made it malfunction less than before, but by the time I got to my gas station two or three miles down the road, it had gone back to really malfunctioning.

And before you say its bad gas, I've been using this station (same pumps) for a while now (its a BP) and have had zero problems with them in the past.

I've paid more attention to all the details now, and when you floor it in the morning when the engine is not warmed up yet, there is a slight hesitation before she goes. But no stumbling at all. When idling (warm, she idles at about 600 RPMs), I'll notice a 50 RPM dip (about every 20-30 seconds or so).

From research online, the four biggest culprits I seem to find with an engine stumbling or hesitating are...
-TPS
-MAP
-Vacuum leak
-Ignition System (wires/cap/rotor/plugs/coil)

I think I'd notice a larger problem at stock tune if it were a wire or spark problem, plus probably a misfire CEL code. The cap and rotor look to be in good shape after a visual inspection, and I tried replacing my Blaster 2 coil with the stock coil, and the Autolite plugs with stock type NGKs. No difference.

A vacuum leak is unlikely I'd think, as its a fresh plenum gasket, Hughes plate, and nice intake manifold. I know its been described before, but can someone tell me or give me a link to a DIY for testing to see if this is the issue? I figured I'd notice more of a problem if it was, but it never hurts to check.

If the TPS or MAP are partially failing, an increase in the timing and what-not (performance tune) may "overwork" them and cause this problem to baloon from a minor hesitation or sluggish response to full out stumbling, big hesitations, almost cutting out... right? Or am I completely off base here?

 

I'm getting about 19mpg right now.. kinda hard to tell because I let it warm up in the cold weather.. I notice that the shift patterns changed and the engine sounds a little "starved"...runs like a dream! I've used the tow haul mode as weel as the performance and they are all awesome! I did mine with the HS 1.7's and a 52mm TB.. so it's hard to tell which added the most power.. but together these 3 rock the socks off my truck!

 

Have you checked your fuel pressure lately? Maybe a clogged filter or failing pump could act that way?

 

Thanks, will check that as well, but I'm hoping thats not the issue. Thats probably the worst case scenario.

 

Anyone else have other ideas, things to check? This wouldn't be my CPS, would it?