I have a highly modified 2000 Camaro with a drivability problem I cannot get fixed locally, my tuner who did the tuning (Greg at Livernois) has no idea, my two mechanic friends have no idea. No codes set, used Snap-On scanner, Tech-II scanner, and autotap. Can’t see anything wrong, no huge amount of misfires or anything unusual. Here is what is wrong:

2000 Camaro, lots of mods….drivability issue and performance issue-
382 Stroker built/installed by MTI, Rossler 4L60E transmission, FLP headers, ORY, no cats, two 02’s in headers, none past the headers (no sims either, tuned out), X1 cam, no AIR stuff, NX wet kit, recent tunning at Livernois Motorsports. Car ran fine until 9-16-04, then it ran for ****! Here is the story…

Car was running fine, changed plugs, changed oil and filter, tranny fluid and filter, cleaned nitrous filter, new fuel filter, did front brake pads, polished out headlights, added metco valvecover breather…
Drove fine, had nitrous in the line (didn’t race anyone that night), shut the bottle and hit the button (ran hard for a second, then flooded with fuel), check-engine light came on, drove it for a few minutes to clear everything out, light went out, felt fine. Next day, too friend for a ride, ran weird, idled high, very unresponsive, rpm’s came up real slow (like an ultra tight converter or something)…tried it on and of the bottle, same response until above 5,000 rpm, then the rpm’s came up faster. When driving, car would accelerate on its own all the way to 45 mph or so and stay there (from a dead stop with no gas being applied), when shifting into neutral at 45 mph, the rpm’s would climb to 1500 or so, and then slowly fall. If you hit it on a 40-50 roll, it would accelerate slowly until 5-5500 rpm then it would pick up speed.
Here is what I have done (unsuccessfully) to address this problem:
Disconnected/reconnected battery after every change-
Replaced IAC with another IAC from a good running, same year Camaro
Cleaned IAC
Replaced TPS
Checked for intake leaks with carb cleaner (none found, no surging at all)
Autotap- no codes
Snap on scanner- no codes
Had friend rev engine to 1800 rpm or so, disconnected IAC (per mechanic friend), car was more drivable down low, did not want to idle high or go to 45 mph on its own, but still felt sluggish (again like a ultra tight converter)
Went to Livernois to have car re-tuned…used a brand new ECM, did the tuning, made good power (dyno pulls were at 70 mph and above) made 580 rwhp and 644 tque so engine is not damaged, and everything ran great on the dyno-
Test drove it and the exact same problem as before with drivability. Tried replacing Metco breather with standard oil cap, seemed to help lower the idle a little but no major difference. Put foot on brake and foot on gas…floored gas…rpm’s went to 1800 at WOT on the brake, did not go above 1800 rpm’s or spin tires. At this point I thought it was the converter, so I shipped it back to P.I. for a check. Everything checked out fine, they rebuilt/restalled to 4000 and sent it back. Put 3.42 gears in rear end, and I believe the computer is now set to not lock the converter at all until 3rd gear at about 50 mph. Now car drives the same, can tell the converter is looser, goes to 2400 rpm on footbrake with gas FLOORED, will not push the car or break the tires loose. Also installed brand new IAC motor, cleaned TB real good. Rechecked for leaks (went through a whole can of carb cleaner) all over intake, TB, basically whole top part of engine compartment.

I will likely have to take it somewhere to get it looked at (I am in NE Indiana), and have sent an email to APE to see if they can do anything. Suggestions?

 

Just finished your post and it's time for a pro, you have checked and changed parts on your ride to the point that experience is all that is left. Good Luck, you'll find the problem

 

I noticed you have nitrous on the car. Is it a dry or wet system? If it is a wet system, the fuel solinoid might be stuck and loading you with fuel. If your mechanic friend has a smog machine he can check to see if you are running very rich. It sounds like you are loading with fuel. Also would clear up at high rpm due to consumption.