ok i have a 1993 chevy pick up 4x4 the motor had alot of miles on it. but was rebuilt to run stroung it tested around 400hp.  it ran fine for the first couple months but now it seems like its like gettin more air then gas are somthin when i get on it to like pass a car are somthin. and it will only do it sometimes and sometimes it will do it a few times right after another and its become a problem when im in heavy traffic so i was hopin that someone would no whats goin on it kinda almost stalls i guess u could say for a sec. any infomation would be very helpfull thanks .

400hp???? you gotta be kidding, on a stock TBI setup?

tell me its a 383 or a 454 with plenty of mods

a brand new stock 350 in a 94 chev pickup came with (at best!) 185-220hp, contrary to what most owners believe, but i have old copies of 4WOR where they were ecstatic that the TBI 350 was putting out 190hp (i think it was a 92 issue....was a shootout, chev vs ford).

with 400hp, you shouldnt have any problems passing......corvettes.

I would talk to whomever rebuilt your engine to solve your problem. 

fuel delivery? injectors? filter? fuel pressure?