I'm thinking your wires and spark plugs may have gone to s***. Have you replaced them or even checked them? Remember, even though you haven't seen the CEL come on, it doesn't mean it isn't there. The previous owner could have simply removed the bulb for it from behind the instrument planel.
Check this out:
VWvortex Forums: mk3 golf bad obd reader
This is a discussion from a different VW Forum that explains exactly how to display the DTC with CEL on the dash. Read it.
I used it to figure out any faults on my Golf.
**THIS ONLY APPLIES TO OBD-I VWs**
Good luck.
