I have been fighting with a 1997 GMC jimmy with a 4.3L. The motor wont rev over 2000 rpm. The truck was given to me, and i have been trying to fix it. Originally it said that the number 5 cylinder was mis-firing it turned out that one of seats were bad so i had the heads rebuilt. I got the thing back together and it has the same problem now, but this time no engine codes. Idles fine but as soon as you give it gas it revs to about 2000 then bogs out the stalls. Any idea's Im not familar with chevy's