........ have K&N filter and 57i aswell?? 
a k&n 57i is a k&n induction kit so the kit is the filter and....
Hey guys
I've got a mk2 1.8 8v gti, it's fitted with a K&N 57i and a Powerflow backbox. What extra power (if any) do you reckon thats given me, and also what would you recommend as the next mod, and why? The engine has done around 150,000 miles and I'm on a kinda tight budget!
Thanks! 
sorry to say this but ditch the induction kit, sell it on ebay or something and get your original box with a decent panel filter (ie k&n, jetex response, green etc) and drill some hefty holes in the wing side of the air box. this allows you to have good filtration with a proper shield from the engine heat. it'll still sound good and depending on what enging your golf has there are a few little tweaks you can do to improve the airflow too.
an induction kit is good in principle but sucks in hot air from the engine (and as cold air is denser, thus containing more bang when mixed with fuel and squeezed!) can actually rob power from your engine.
i had a green induction kit for about 2 days before deciding it sucked and about a year after aquired a k&n and that lasted under a week. trust me on this!!!!!
so i'm afraid with your current mods chances are your under power or not alot better.
to get more power out of an 8v you need to go with good induction (ie good cold air through modded air box) good exhaust (full system, ported manifolds if you can be arsed and maybe larger downpipe) and then polished/ported/gas flowed head combined with a decent performance cam.? but bear in mind on a high mileage engine it could put alot more stress on the bottom end.
i don't mean any of this to put you off as i have an 8valve and love it but at the end of the day they aint super fast!!!! good luck with it and stick around for lots of tips that'll come up. have a look back through this section because we ran a thread about cheap/free mods for mk2's
