I have been struggling with this problem for about 2 years now. I had the motor rebuilt after a shop dropped a bolt down #8 and beat the heck out of everything.

Here is what is done to the motor:
383 Stroker 10.5:1 Compression,comp cam, ported heads,5 angle vavle job, 2.02 intake and 1.6 exhaust valves, ported plenum, Ported and siamesed runners, TPIS Big Mouth Manifold with EGR delete,MAF Descreened, Underdrive pulleys Holley AFPR, MSD 6AL, MSD coil, MSD 8.5mm wires, Bosch 30# injectors,255 LPHWalbro fuel pump, Vortex Ram Air, Air Foil, MAT Relocation kit, TB Bypass,Heated 02, Dual Exhaust, 2400 RPM stall torque converter.

So basically the car ran okay at first. I had a holley AFPR fail on me and since then the car has never ran right, missed at high RPM. The fuel pressure was set originally at 55 psi, which I thought was very high. Well I replaced the AFPR and this problem has been bugging me for 2 years.

What I dont understand is what is actually happening, the motor runs strong all around except around the 5k range. Then basically it falls on it's face. After the tranny shifts the motor does recover and go like crazy until the next redline.

I thought it was fuel because when i turn the fuel pressure up the problem gets better, so I installed 30 lb injectors opposed to the 24 that the motor was originally built with. Well I have the fuel pressure up again around 50 psi or so and the problem remains.

I had a custom tune done on the car, and I even sent the guy scans using datamaster to burn a chip. The problem still remains. So basically I am wondering what is going on here. Is there actual spark knock occuring. I have been through the ringer on this one. I have put new plugs in the car, and then checked them and there was no sign of detonation. The problem exists whether or not I have the knock sensor plugged in.

I have been looking at the scans and noticed that the computer will only pull 6 degrees of timing. Right when I jump on it it will pull timing, and then at redline it pulls timing. There is a setting in the tables "maximum knock retard in power enrichment mode" which is set to 6. So does this mean the car is always pulling timing, or does it mean the car is really detonating and only able to retard 6 degrees?

I have tried race fuel, but I may try it again. Sorry for the long post, just basically running out of options. I have never been one to ask for too much help but I have fought this one long enough and I just want to enjoy the car.

Thanks again,
Craig