hi guys wondering has anyone fitted to their st170, my car has 81k on it and is a 2002 car so im going to be pulling it into the garage some saturday im not working on anything else and putting a kit on it, but wondering if would be worth my while to buy an adjustable exhaust cam pulley, is there a noticable power difference by adjusting it? is the fuel economy reduced by much? and can i adjust it myself? i am a qualified mechanic by the way