Vehicle is a '90 Chevy truck with a 5.7 (it is stroked to a 383) w/approx 40,000 +/- miles on it. The problem is that the engine will not run right, it idles rough and when you start to accelerate it really stumbles at begins to backfire thru the TBI unit (Approx 1500 up RPM) it also appears that the fuel is being blown back thru the TBI unit also. This engine was running great until it was swapped into the current vehicle. It has new lifters, pushrods and rockers (valves have been adjusted hot w/engine running). The timing is set to factory specs. Alll electrical (ignition and emmission related along with the ECM) components are new (it was doing the same thing with the old components installed!). It was a new timing chain also. The computer is not setting any codes. The compression in the cylinders is good and even throughout. I am stumped at this point any help/advice would be greatly appreciated.