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Message: <blockquote data-quote="Lee12609" data-source="post: 751362" data-attributes="member: 12415">the PI intake valve just has extra material below the seat ring, so there is less PTV clearance than a stock npi intake valve. exhaust valve is bigger, and the port flows better in stock form, so with stock npi exhaust port the bigger pi exhaust valve size is useless. its the ports that make the flow so much better than npi's in stock form.i've been debating staying NPI when i build my longblock, so i've done alot of research. hardcore npi guys swear they flow as good or better than ported pi's, and some people have flowbench data showing such results, but i've only seen a handful of porters that are capable of getting the npi's up to par, and to get there it cost more than a set of stage 2 PI's. so, i'm still undecided for now.... might just end up going trick flow...</blockquote>