Hey. I own a 99 GMC 3500 with a 5.7 enjine. This is my work truck that I use everyday and I carry alot of weight. Power is pretty good and I average 7.6 MPG. I reciently bought a 94 3500 as a backup. It is a 5.7 with the older T.B.I. I'm averaging about 7.1. The 94 with the T.B.I. has an incredible amount of power. That truck doesn't even know when it's fully loaded. I don't need that much power. I Never accelerate hard i feel that would be asking to muck out of the tranny or differential. Since I don't need that much power it seems I could use a smaller T.B.I. or something. I feel that would increase my gas mileage or would I mess up the computer orthe emissions? Or is there anything else I can do. Any Help Would Be Great. Thanks

 

TBI is not better in any way compared to multi port fuel injection.
Fuel injectors do not live forever. Have your engine analyzed. You could have a a problem that is killing your power.

 

are you experiencing any lack of power with the 99? Clogged cats could be a source of worse mpg, and lack of power.