It is 7:45 a.m. in Arkansas and I just got off the phone w/ the mercedes service department. I explained that I would like a scope test before pulling the heads. The technician explained that at this point they know that it is a valve problem- nothing else cause compression problems. Basically, they are going to do $600 worth of work and now I feel he is angry. I hope they are honest. Have a good day! Angie