2000 golf trouble codes

I've been driving with my check engine light on for over a year now and it keeps throwing the same code. Fuel system to Rich and Fuel system to lean. The car drives fine and I've not sacrificed performance or fuel economy but I'd like to get this resolved.... Without throwing parts at the car ($$$) what could be causing this? I've never changed any of the sensors O2, temp or MAF. Used a buddies Vag-com to get the codes but no direction on what sensor could be failing..... Help!?!