My 91 300zxtt is having oil leak from the solenoid valve area on both banks. I'm attempted to replacing the valves but it's stiff. Anybody know how to remove and how to install? From the Service Manual it looks like there's a key to the shaft. My engine has 207k on the original engine and no other leaks or oil burning. Compression 140 - 155 psi. Great engine but pain to work on. I really enjoy reading this site.