vocky as with most engines, it is restricted by the manufacturer to prolong engine life the biggest problem with the 'direct' is there are few tuning options, but a decent cat back exhaust and panel filter + cold air feeds will help it breathe better
rushy I just think the vec c is just a bit heavy for the z22, its got good legs though but getting up there I find it a bit slow. Bet it goes like stink in the astra though?