Intake manifold swap

I was just reading about someone who swapped a '99+later intake manifold into his '95 XJ and was wondering, is the same swap possible for an earlier model, '88, with the six? The claim is that the newer manifold had better flow, larger plenum, etc and there are claims of a zillion horsepower gain and all of that. Curious as I am going to be changing my exhaust manifold (yup, it cracked) and figured what the heck, if it works I'll give it a try and see what happens.

Will not work because of the fuel injectors and extra sensors on the 99 intake. You veh. is pre-OBD1 so I'm sure it will not work.