[Formula413]

The difference between stock exhaust and a Loudmouth is probably around 10hp, if that, which you probably would not feel. It's unlikely that someone would have the car tuned for a catback, usually a tune would not be needed until at least long tube headers have been added, if not internal mods as well. And the difference between a paper air filter and a K&N is maybe 1 hp at most. However replacing the stock airbox with an aftermarket lid is usually worth about 10 hp. If you got a lid and a catback that was more to your liking (Maybe Magnaflow or Hooker Aerochamber) you would probably gain 15-20 hp and might see some SOTP difference. As for watching fan activation temps, the stock temperature gauge is essentially a dummy gauge, to see at what temps the fans come on or off you would need an OBDII scanner.