Off Idle Stutter 5.7 GRRRRRR

I have been troubleshooting an issue for some time now, and have finally decided to tell the world, surely someone can help.... This pickup has an off Idle, in gear, dead spot-stutter-stumble. You can drop the hammer and it will go, but if you ease into the gas when you first take off it will hesitate and stumble. The hesitation is not noticable in Neutral.

I have a 1987 Chevy 1/2 ton 4x4 pickup, I swapped out the original 305 with a 350 out of a 1990 chevy pickup. Before installing the engine I fitted it with forged pistons, and a balanced rotating assembly, an Edelbrock TBI cam, and aluminum roller rockers. The exhaust system consists of Edelbrock emmissions legal hedders, and a full Dynomax 3" system including hi flow cat and super turbo muffler. The heads are 350 and have been rebuilt and some slight port work done. Compression pressures are within specs and real close from cylinder to cylinder.

Through out troubleshooting this off idle stumble, I have installed an MSD hi energy coil, a new proform distributor, and a Holley hi flow throttle body. None of which help the situation.

I have installed new sensors : knock, map, O2, CT, and have tried 2 different factory 350 throttle bodies, they all have the same results. The Ecm has been fitted with a Jet performance Stage 2 chip, and also tested with a factory PROM also.

I have checked fuel pressure and it is within the specifications of a chevrolet tech manual.

THe ECM has set some intermitten codes, one rich and one lean. THe engine seems(smells) to run rich at an idle(especially with the Holley Throttle Body) and has set a lean code on a few different trips, driving 55 where I had no extra weight on the pickup..


Exact cam specs.
Int Exh Int Exh Int Exh Int Exh Open
244° 264° 194° 214° 0.265 0.294 0.398 0.442 10°
Close Open Close Lobe Seps. Intake Ctrline
ATDC 24° ABDC 44° BBDC 10° BTDC 112° 107

If it makes any difference the truck has a 700R4, 3:73 gears and 35" tires. Cruising speed RPM is in the 2500 range.

PLEASE HELP---- SOMEONE??????

http://www.imagestation.com/picture/sraid61/pbd650c220fbd80c69f862ede146177f0/fc31ea20.jpg

dont know if u have fixed it yet............ check the copmuter itself.........if its the 305 comp u need to repace it with a comp. out of a 350 equiped truck.

You need to check the basics. First, why is the engine running rich? Does the O2 sensor reflect this rich running? If not, is the O2 ok? Let's start there. Hopefully there are no issues w/ EGR. You might try disconnecting the hose, to disconnect this device. Let's do one thing at a time, give me the results and we'll proceed slowly. Guessing will simply cost you money. Ray