I had TBI on my 88 silverado and it was great. Nice power, good torque, never had a problem with it really except once when the gasket for the injector housing failed but it was an easy fix. I'd rather have multi-port also but TBI isn't bad at all really. But you can get better mpg with multi because some gas will evaporate on the throttle plate in the TBI housing but not all that much to notice. That's what i hear... Mine was a TBI 350.

 

I had a 91 blazer that was the vortec 4.3 i changed the intake and put a carb on it and used a older dizzy and took the ecu out it ran a lot smoother and i only lost about 3mpg.