I'm selling mine (I know its standard so not quite comparable to your 300bhp beast any more) and have put everything back to standard ready to sell, and I have to say, I think it is much more responsive with the factory airbox back on.
Low down in the revs the standard box should be able to flow plenty enough for a standard or mapped engine, so if you are only doing short journeys you may well be better of going back to standard intake...Once the engine is up to speed I wouldn't be suprised if the standard box is too restrictive for your engine and you may well notice it loosing you power though...
Low down in the revs the standard box should be able to flow plenty enough for a standard or mapped engine, so if you are only doing short journeys you may well be better of going back to standard intake...Once the engine is up to speed I wouldn't be suprised if the standard box is too restrictive for your engine and you may well notice it loosing you power though...