You can try running multiple cans of seafoam or b12 through the gas and intake, but that may only be a temporary fix at best. He set up a water injector but it only masked the problem, and the head eventually had to come off.
X2 Clean it all up, carbon buildup will mess stuff up big time! I've seen it up compression enough to ping/knock off of cheap 87 octane fuel.... PITA but thats about all you can REALLY do to correct the issue... how many miles are on the engine???
