I recently bought a 00 reg irish WRX and decided to confirm its HP before I did any modifications to it. Car is running fine and with standard exhaust but the rolling road (martin treacy) is indicating 200 HP. Were these expected to produce 220hp with the standard exhaust ?. There is a k&n filter fitted and car was recently serviced. I have a full decat exhaust for it but dont want to fit it as its too loud. Any ideas how to recover the lost horses ? .