Recently I changed a 1991 K11500 from 5.7 TBI to 5.7 TPI. I have the engine running but have a problem. Rolling idle (intermittent die at idle)and lack of power. I used the TBI ECU and the TBI map sensor. All the other sensors and switches are from the donor car and engine(1987 IROC Camaro. I have tried several things to get the idle to straighten out with no success. The owner of the truck states that he had the same problem with the 5.7 TBI.I am leaning toward the MAP sensor or the ECU. It appears that the timing is advancing and retarding during idle. The vehicle seems to run great on the road. Any help will be greatly appreciated.