I just bought a baja 232 Islander and it has a 454 MPI, I was wondering if there would be any performance upgrade in switching the intake out with one from a Mag motor?

no benefit in fact it might actually decrease performance. The mag MEFI might give a little more timing and would raise the rev limiter but then you are looking at cleaning pieces of the cast crank out of the bilge.

I understand what you are saying, was just wondering if they are a little more free flowing and also wondering if the stock fuel injection and computer that I have would work with it.