P0506 Fault Code 1999 MK3 Jetta Help!!!!!!

I have a 1999 MK3 Jetta and when checked this fault code P0506 came up. My jetta used to stall out when I pushed the clutch in sometimes and when I checked the code it had a P0102 code. I replaced the MAF and the light went out. Now 3 days later the light came on again and it was P0506. The RPMS rev between 400 and 600 when the A/C is on but it idles fine (around 900) when the A/C is off. This car is really pissing me off. Anyone had any problems like this with theirs or anyone know what I need to check. Please help me out I am getting pissed and might drive this piece of shit off of a cliff. Thanks Travis

Idle control system rpm lower than expected. Check for lots of carbon/oil buildup on the throttle body. ALso check for vacuum leaks.