Revo are increasingly finding that on many modern performance cars, the factory airbox is quite well designed and not limiting the volume of air that can be taken in by the engine at Stage 1.More often, where restrictions are to be found was in the pipework behind the air box.To that end they've starting offering these OEM plus intake upgrade kits.Revo start by replacing the pipework from the air box back to the turbo. Because the factory part is plastic, it needs convolutions in the walls (ribs) to allow it to flex. Revo replaced this pipework with a perfectly smooth one piece aluminium pipe. They were also able to better tune their pipe, again to improve flow and reduce turbulence. This gets more air to the turbo quicker, improving flow rate and reducing lag.Revo also replace the paper filter element with a higher flowing three stage foam filter. The three layer foam construction absorbs more dirt for longer before the filter gets clogged.This upgrade kit still sees significant gains