I have recently purchased a 88 Comanche with a blown head gaskets I replaced the gasket installed new lifters and replaced majority of the vacuum lines it cranks up just fine maybe a slight high idle and when I drive it it does fine until I slightly let off the gas then it starts jumping real bad and runs rough I can't just Cruze on it you have to be to the floor or let off completely for it to run fine any idea would be greatly appreciated!