AvantcrazeS6

If I do not have any error codes on my O2 sensor would you replace it at 65K per the service manual? Also will a KN air filter help performance that I would notice? I dont think I want to bother with the cleaning of them so how long will they last?

Mr.FRU-T-Pants

I would replace it routinely, yes. Every 60k or so would be a bit of overkill, perhaps, but just to be on the safe side, I'd change it whenever I had the timing belt done(every 60k). That's me. I like my cars to run well.

As for the K&N, IMO, on five cyl. cars, it does nothing for performance. It does save a little cash in the long run, if you keep the car long enough, and is a good quality filter element, which you can clean as often as you like. Be careful not to over-oil the element after cleaning, and you should have no problems. A cone filter would be better suited(K&N makes one), if you can effectively control/isolate it from heat soak of the turbo with a heat shield, either homemade or otherwise. That might afford some extra flow and build your boost a little faster, and sounds pretty cool as well.

FWIW,
Fru-T