Well, after yesterday's events at Bradenton (sucky time slip, car felt like crap) I decided to take the car out today and do some logging so I could adjust my PCM fuel trims at part throttle, then move on to full throttle again.

I found that when I get the car up to around 4500-5000RPM at part throttle (about 20% to 30%) the car just falls on its face. It's like it hits a brick wall and doesn't want to go any higher. I have to give it quite a bit more throttle to increase the RPMs. Happens in gears 1 2 and 3, didn't try the other gears, but at least that shows (hopefully) it's not a drivetrain thing.

The RPM it hits at changes, it seems like at lighter throttle I can get it to hit at around 5000, at heavier throttle it hits earlier.

Would valve float, related to bad springs maybe manifest itself this way?



Car is a 383 stroker with 9.0 compression, Turbo kit, heads cam etc.


Plugs seem fine, and I gaped them correctly.
Not a boost leak because I am only at part throttle.

 

i had something like that before (although not near the mods you have) and it turns out the map sensor was bad.