[s-cars] New timing belt is in - now car is acting up

[David Forgie]

As per the previous suggestion, your PCV system has a problem. Most likely your one-way bleeder valve under the intake manifold has failed and boost pressure is making its way back into the 
cam cover. 

Have a good read on this: 

AAN/ABY/ADU Positive Crankcase Ventilation (PCV) System with revised diagram, PNs and Links: 

http://forums.quattroworld.com/s4s6/msgs/22506.phtml 

Dave F.