Fuel pressure and knocking?

if you have been running premium fuel for years the problem is carbon buildup on the intake valves. the extra detergents in premium fuels keeps injectors cleaner but the injector sprays on the hot intake valve and those additives build up and "glow" causing pre-ignition and pinging. the problem is called "christmas treeing" because the valve looks like a christmas tree with all the carbon on it! kits are available that hook up to a vacuum port on the intake and suck in the cleaner then shut it off and soak for 30-60 mins,while you wash out the TB with the spray.