Check the plugs and if they smell strongly of fuel it could be that the car is overfuelling. Alternatively it could be running too lean and not fuelling enough.
There are some checks you can quickly do, (i had a 16v so i'm going according to mine, yours being an 8v K-Jet should be similar in set-up)
First up is the WUR Warm Up Regulator, sits on the RH side of the engine and has an electric connector, 2 fuel pipes and a vac pipe going into it. This regulates fuel pressure dependent on load and engine temp. I think on the 8v K-jet it sits on the front of the block.
Unplug the connector and read off the loom if its getting 12v with ignition on.
Measure the resistance of the socket on the WUR unit (not the loom) and it should be around 22ohms.
Wont hurt to change your fuel filter if it hasn't been done to your knowledge
And, most common with VW's, coolant temp sensors. I know there are 3 on a 16v but I'm not too sure on the 8v