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Hope im not disliked too much for asking this on here :D, but around what level does the standard SR20 head become restrictive? The 180 i just bought has 355rwhp on pump fuel @ 25psi which i thought was quite high boost for that sort of power... it has:

hks t300 turbo, hks exhaust manifold, hks wastegate, toda step 1 cams, subzero 80mm sub zero throttle body, sub zero plenum, wesico forged pistons, gapless rings, arp rod bolts, 600x300x70mm PWR core intercooler, 3" exhaust with gutted cat. Its obviously not too bad because 355rwhp is pretty good, but the 2 things that stood out to me were the 3" exhaust, and the un-modified head and was really wondering if there would be much point getting the head ported, and port matched to the manifolds

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I know, i love the RB's, but ive lost my hatred towards SR's now :D Im pretty impressed with how it goes, and there are some things like the head, intercooler, and maybee look at upgrading from a 3 - 3.5" exhaust.. If it stays like it is now i'll still be happy as its plenty quick. The good thing about this is that you wouldnt expect it to go quick because they are all SR's and sound the same when going slow, when you hear an RB in a S13 you know it will go pretty good.

A workshop did a test for HPI they flowed tested them and came to the conclusion that at 30psi they could flow 100hp more airflow according to them. But at 25psi you may get 50-60 hp out of it. Considering head works not cheap it'd b happy with what ur car has, but its not my car, (unfortunately).

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