LS6 Power Issues

[Mgodsy]

Hi everyone,

I have a 1968 C10 that I have done an LS6 conversion out of a 2004 Z06 corvette and an 4L60E trans out of a truck.

The problem I'm experiencing is that when the engine is in park it runs good and has good throttle response. It sounds like a beast. But, when I put it in drive and give it gas it cuts out so bad that the truck will hardly move. I get no trouble codes on the scanning tool.

I'll list what has been done to try to make this simpler,

I purchased the LS6 with the computer and wiring harness. I sent the harness and computer out to be configured for my truck. The company that did the wiring and programming also changed the throttle from DBW to Drive by Cable and I changed out the throttle body to a drive by cable.

-I have replaced the plugs and wires
-Verified firing order
-Verified fuel pressure at star, under load and at idle. Consistent 58psi
-Changed fuel
-The new wiring harness only has 4 wires for it to run: fuel, key on power, constant power and fuel pump. Also has a ground. I verified the wiring was hooked up correctly
-I get no trouble codes on scanner


Again, when the truck is in park sounds like a beast, as soon as I put it in drive and give it gas it just falls on it's face and barely has enough power to move the truck. It runs very rough when in drive and giving it gas.


Any help will be greatly appreciated!!!