Mk1 golf cabi major help needed asap

Hi,can anyone help me here? My mk1 golf runs and starts fine when cold,when the oil tem gets to 90 ish it starts playing up.If i keep the revs up at junctions etc its ok,if the revs go to tickover it cuts out,or runs on 3 cylinders,cuts out again.Hard to start,coughs farts etc,but its not to bad above 2k revs. Sometimes judders driving along,but cannot stop at junction or roundabouts without cutting out,hard to start,3 cylinders etc.

Anyone else had this?

Its a 1990 gti cabi,all standard.New plugs,fuel lift pump etc
Also are all these cars bad when its been raining? took me hours to get it going today!

Could be lots of stuff, but I'd check for these first:

Excessively weak mixture, covered during warm-up by the richer mixture required from cold.

Low system pressure* in fuel metering head - the spring in the primary pressure regulator* gets out of adjustment, it needs shimming by a Bosch service agent. The symptoms are similar to what you are experiencing, as the low pressure is covered up during warm-up by the higher control pressure* provided by the warm-up regulator.

*look at Domain parking page for more info on these concepts.

Of course it could also be an electrical item breaking down as the temperature under the bonnet goes up - coil, HT spark plug leads, etc, especially as you also mention that you had more trouble than usual in the wet weather.

Thanks for the advice,i'll get it check out asap
ben