[Last930]

I recently had the AOS replaced on my '04 Boxster S; once that was done the RMS started leaking. Today I saw oil fumes coming out from the oil filler cap with the engine idling and fully warmed up. I opened the cap and there appeared to be a fair amount of pressure in the crankcase. What could cause this? The engine has 95k miles and runs great. I don't think it is a ring issue because it runs so well and has had consistent oil changes.

Is there something that could be missed or reversed during the AOS replacement that could cause this?