I agree 100% with Aragorn. Change the stat before the sender. Those are the exact symptoms my car had. Let me guess, with the heater on it takes longer to get up to temp/temp drops down when you put the heater on! Stat buddy. Deffo! Your lucky its not a v6. Cambelt off job for a stat most of the time! Should reach op temp in under 3-5 mins. To find out how to do it (I'm using my iphone mate, otherwise I would put a link in) go to audidiy.com , select b5, select engine/mechanical and you should find something there. Failing that do a search on this forum using thermostat as your search/key word. Good luck duck!