wondering if you gain any hp/torque after the quicksilver. or too low to notice?I drive a modified 1.5L and have looked into intakes and exhausts. The OEM air box should be the same up to the downpipe. JCW models get a larger intercooler, but the airbox to the MAF sensor should be the same. In the aftermarket scene, most Cold Air Intakes or cone filter set ups should work. Stay away from brands like Eventuri, however, or you'll end up having to install a hood scoop
As far as exhausts, most will not work because of the dual exit on most S models. I suppose if you changed the rear bumper, you could maybe retrofit, but not sure. I have a Quicksilver Exhaust System from the UK on mine. Sounds fantastic IMO and really brings out the 3-cyl. character. I might be one of the only F56 1.5L with that system in the states, though. They're a bit difficult to get around here due to having to import.