Q-jet Problems

[Whitelm]

Okay, I have waded through alot of questions and answers but I can't find anything that comes close so here goes. I ordered an new (completely re-built) Q-jet carb for my 71 k-10. I installed it and set the timing. It purrs like a kitten when idling and revs up great in park or neutral, but when I stick the truck in gear it loses power and eventually stalls when I push on the gas. I have installed a new distributor kit and fuel pump. Fuel tank sending unit is also new. The truck was running fine when I pulled the original carb.
Any ideas??