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IMO the damage would have happened on initial start up after a carbon clean. I believe his valves were cleaned months ago. He also posted data logs showing good timing advance and airflow numbers post cleaning.

IMO, it's something other than a shoddy carbon clean.

Data log intake temp and ignition advance with and without water injection

Based on those and other pictures I've seen, the deposits don't appear to be self limiting as postulated here.

Let me explain further. Based on my experience remapping Mitsu Evo, Subaru, and GM LSx ECU’s there are at least two ignition maps. They are typically known as low detonation and high detonation ignition maps. When the knock sensor triggers a certain threshold the ECU reverts to the high det map. T...

any pre-ignition, consistent in nature, like deposits, will set codes... this is how it works... the ecu sets operating parameters or 'setpoints' for: fuel rate (metered jets in the old days, now pwm injectors) timing (vaccum or the good old Bosch -008 mech advance, now computer driven coils cam ph...

Arthur, Why do engine tuners spend endless hours on a flowbench trying to extract the most flow from a cylinder head? Also you insist that you have proven that carbon build up has no effect on performance. I have read your posts here and on on other sites and yet to see any conclusive evidence that...

Arthur, Why do engine tuners spend endless hours on a flowbench trying to extract the most flow from a cylinder head? Also you insist that you have proven that carbon build up has no effect on performance. I have read your posts here and on on other sites and yet to see any conclusive evidence that ...

Nonsense. A restriction is a restriction, whether it be at the air filter, throttle, manifolds, valves, catalysts or exhausts. A build-up of debris on the valve will restrict the airflow and thus the density of the combustion mixture. For maximum power it is important that everything functions as i...