I think you will find that you have a vac leak somewhere. I took the tbi off my 4.3 and put it on my 3.4 tonite just to see what would happen. It idled like crap,smoked like a train. HHmmmmm guess what it was? Throttle Body gasket was cracked. Put on a new one and all better. I found this by spraying starting fluid around the tbi unit. Just for shits and giggles you might want to try that?