Theoretically since the largest maf out is 85mm it would restrict the 90mm lsx manifold and throttle body? youd still probably produce more power but wouldnt see the full potential?

 

Whatever piece in your intact track is the smallest/least flowing part, that is your restriction. If you currently have a stock TB with the 85mm MAF, then the new 90mm will help you, but the MAF becomes your restriction. This assumes your engine can use the air, which it probably can to at least keep the manifold primed for each intact event.

Todd