How much difference will these parts make? TFS and exhaust

My buddy has a 93 gt hatch. It has a 70mm throttle body and egr, original headers, e or x cam (he is not sure), 3.73's, a 2.5" exhaust from the headers back to flows with dumps (no converters), and underdrives. Other than that is is stock from what we can tell. I just gave him my equal length shorties and TFS track heat intake to try. I think the headers are going to make a huge difference, espesially if he puts that intake on....what do you all think? He runs 8.88 in the 1/8th now on decent street tires.

any opinions at all?

he had ported his stock intake and his et actually when down a bit and there is a part throttle hesitation now. i figured by porting the stock intake he may have increased flow capacity but decreased velocity. and since he had the stock exhaust you can only take in what you can blow out....ya know