rough running G60

90 G60 Corrado runs good until it warms up then it starts running rough. barely idles. changed O2 sensor and temp. sensor and it ran fine for a few days then went back to running rough. nothing comes up when codes are checked. any ideas or help is greatly appreciated. i don't have much hair left to pull out.

Check the Idle Stabilizer Valve (ISV). It may be loose, if so, tighten it. If it seems alright, you might go ahead and replace it. Although I think VW charges a fortune for them