heres my problem i got a 4.3L v6 on a 99 silverado. i brought a 5.3L v8 (junk yard it was a stolen truck insurance job)i got it complete with engine harnes and computer. i try to start it and it starts but dies immediately. and the only way it will stay on is with starting fluid. so they told me it was the computer so i went and brought another computer(junk yard) and it did the same thing. so i need some help thanks