I have a 2001 1.8GTI and it does the same mate. It seems to have got a little better over the last few months (Weather related?

), it does seem worse when it has been raining for some reason?? I've also changed MAF sensor, Plugs, Thermostat, Fuel filter, various lengths of pipe, de-cat. Engine management light keeps coming on, code something to do with thermostat. I reset the code and sometimes it can go 3 weeks before the light comes on again, some times it can come back on with in a hour???
VERY STRANGE