I just bought a 1990 4.0L I6 engine for my 1994 jeep cherokee. some of the parts are different. can i put the intake manifold from a 94 on the 1990?

The intake and exhaust manifold will fit,maybe it will need to be adjusted as far as the holes go,I found they wer almost the same but I had to round out one of the holes on the intake. If you are just trying to use the intake and not the exhaust,I think you will find that much harder getting them to match. The exhaust from a 94 will not fit the 89 without replacing the exhaust pipe.
I put a 91 in my 89 and had to use the intak and exhaust from my 89.