You have the exact problem I had, I went through 3 of them PRV valves, the crankcase breather valve breaks them quite fast, as this is what will be causing the problem


My car runs like its brand new now, the crankcase breather valve is only about £15, if you can fit it yourself great, I dont think its a time consuming job, its getting to it that might be the hard work

When mine was replaced, Audi replaced the T pipe that it was connected to as they said it was very brittle.

I can give you the part numbers if you wish that I had changed


Andy.