Beams performance parts?? Options

[BonzaiCelica]

So i know i dont have a beams engine or an ss-III for that matter but im doing the swap in a couple of years. I was looking in the parts database. Well specifically the exhausts and headers. for all the the exhausts like the hks and 5zigen or any other ones it says that it will not fit the beams engine. the same goes for the headers. Why is that. i thought vvti only uses its main power from the throttle body. So why is it saying it wont fit with those exhaust parts. as of right now i have a magnaflow exhuast which i know is not the greatest with 2.25" exhaust piping. what size does beams engine use for exhaust piping??

[delusionz]

VVT-i on the exhaust camshaft helps expell exhaust gasses at high velocity in the low rpm without restricting exhaust flow in the high rpms.

Restricted exhaust means extra friction to the exhaust stroke (4th stroke) which robs engine power and high velocity exhaust gasses also reduce friction aswell as help out exhaust extraction (where the pulse of one exhaust shot creates a vacuum behind it sucking out the following exhaust pulse)