BMC CDA's are known for reducing performance, the stock airbox is superior to it ,
fit the jetex, they're highly recommended on SCN
Absolutely true, we have a member on a dutch Seat forum who whas a conversion to a TFSI K04 turbo, running 380Bhp and he runs with a stock airbox + paper filter (modded the side, bigger opening). He used to have a BMC before (with lower power figures)