So I was looking at my repair manual and its says that the 89 318 tbi has 120 hp and 245 tq with 9.0 compression and the 90 has 170hp and 260tq with 9.2 compression. Its that due to the computer better tuned or just from the .2 rasie in compression. And if it si the computer tuned, if I find one can I just hook it up and get maybe 160hp??

 

The computer is not capable of increasing compression that is strictly a "mechanical" function of the assembly of the engine, piston height in bore, piston dish\dome size, combustion chamber size, cam shaft spec's.

If you compare the computer part numbers chances are there is very little difference between them between the various years TBI's system were used. There is a difference between the 318 and 360 computers.

Unfortunately, the Mopar TBI computers have basically no "tune-ability"

 

Hmmmm. I've never heard that. I've always seen 170 as the quoted number. 120hp is 5 less than the 3.9 v6 from 87 to 91.