i just bought a 87 suburban with 350 and tbi on it. i pulled the motor because it was blown. and put in a 97 vortec 350. with a GM intake so i could run my stock TBI setup. after getting it all done. now when i come to a stop light. it slowly idles down and chugs until it stalls. ANY IDEAS?? it also did this when i had the stock motor in it.