If it is an EFI type system maybe one or more of the injectors are bad. The seals can go bad and they will alllow tooo much fuel into the combusiton chamber. Make sure the fuel pressure is at its specified PSI, or that will cause problems too if it is too high.
So check the fuel presssure and make sure it is at specification. The fuel pressure regulator could be bad, I looked up the part number, it is 605133390.
Your car shares a lot with the 1.9 gti. I looked in several places and found that people with the same problem had bad injectors or air flow meters.
So, I think if fuel pressure is okay, then the next step would to rebuild or replace your injectors. There is a place called RC Engineering which you can look up on the internet. They will take your old injectors and rebuild tham and balance them and give you a printout of each injector to show its flow and then you can determine which cylinder to put the injector in by usining the best compression of each cylinder. The Higher the compression, the higher the flow rate of the injector that you should instal on that cylinder.
I hope this helps you out. I think making sure the fuel pressure is set correctly and that your fuel pressure regulator is working is very important. Do that before you do anything with the injectors. After you have set the fuel pressure and are sure the fuel pressure regulator is working right or have replaced it, then see how the car runs. You may not need to replace or rebuild the injectors if this fixes it. If it still runs rich, then you should consider replacing or rebuilding the injectors.
Let me know how it goes. It sure has been a long time since you last posted to this question. Over a year.
Please consider a to help us answer more questions.
Thursday, November 1st, 2012 AT 1:49 PM