1992 Chevrolet Silverado Recently Changed Engine 4 3 5 7 Wiring Same Had Air

i recently changed my engine from a 4.3 to a 5.7. the wiring was the same but the 4.3 had a air pollution system. the 5.7 does not. i didn't seem i had to change the ECM. cant get the truck up to performance nomatter what i do to it. is the ECM different between the 4.3 and 5.7? i put a new TPS,IAC, and oxygen sensor on and did not have much of an effect on the performance. could someone help me out on this ? i try my best to do my own vehicles myself cause i cant afford to take it to a shop. anyone's help would be very much appreciated.