there was another thread today asking about what filter, but Martyn's sticky at the top of the mk3 section covers everything you need to know about the most popular air filters
at the end of the day its just an air filter, VERY minimal gains regardless of what anyone says. I had a dynatwist, sold it and now i run a 40quid piece of kit which might not have the greatest flow capability but others that have the same kit probably would agree that value for money its the best piece of kit around
and you get a wooooooooooooosh too (on a turbo)
some air filters are just blinged up so they seem worth the extortionate price tag