Engine light /code 302 on 2000 Volkswagen Jetta

I have a big problem, code 302 which I was told miss firing on the number four cylinder. I took it to a local shop and they could not get the code to clear after checking or replacing wires, coils, injectors. They did not charge me and told me to take it to Volswagon dealership. Voltswagon is now looking at the car. they to now has had it for a week and haveing problems fixing or clearing the code. They are now going to look inside the block for problems using a boroscope, three cylinders has a higher compression than a new car. The fourth cylinder number 4 compression is good but a little high. They are thinking carbon deposit build up or oil getting past the rings. I just had the head done, replacing one valve that broke due to a timing chain breaking. This was done in November of 2009. I did not have a problem till now. The car dose shake as if there is a vacume leak. Still waiting from the dealer on what is wrong. before we took it in the car was running good, it seems with all these test now it runs worst before, it does not run like a car with a bad engine and it does not smoke. Do you have any idea what might be going on with this miss firing problem?

Asked by for the 2000 Volkswagen Jetta