Does the engine misfire? - it could be a blown coil pack. This is what happened to my Bora. Have a look at :-
formatting link
states :- "March 2003: Ignition Coils - Important Information
It has been reported that misfiring can occur on vehicles with 1.8T, V5, V6 and W8 petrol engines and can lead to erratic engine operation or reduced engine performance. The problem is caused by an electrical fault in the ignition coil and in no way endangers the driver or the car. We have not therefore, issued a recall notice in respect of affected vehicles as this is not a safety related issue.
This type of ignition system uses an ignition coil for each cylinder. Should a failure occur, one cylinder will fail to provide power. At this point the engine management warning light will be illuminated instructing the driver to drive to their nearest Volkswagen retailer.
We acknowledge and sincerely regret that some drivers have been inconvenienced and wherever possible, we have and will continue to provide a loan car whenever a customer's vehicle has been awaiting replacement parts.
Customers will not be charged for these repairs.
If you have experienced this problem with your vehicle or your engine management warning light illuminates, please go to your nearest Volkswagen retailer for assistance. "
I got them to change all 4 packs when I took mine in.