I dont know the service history of the car, so start with the basics.
Check the air filter.
Check the exhaust is not choked.
Change the fuel filter.
Clean inside the throttle body.
Put some injector cleaner/fuel system treatment in the petrol tank.
Have you been running it on supermarket fuel? If so give it a few fills of decent petrol, preferably from a busy filling station so you know the fuel isn't stale.
Check or change the coolant temperature sensor (the one for the engine management system, not the one for the dashboard temp gauge).They were always failing on my VWs.
Clear the rubbish out of the boot and only let skinny people in the car!!!
All these things are free or cheap (except the petrol) and are DIY-able.
Are there any other problems, e.g. overheating, losing oil or water, misfiring etc.?
victor, May 2009