I just heard that the hardened seats are for unleaded fuel if it doesnt help I dont care. i am afraid the springs may be a problem I wasn't on or anything just motoring at low rpm's and ping it was gone . i may just change them and clean it up and re-install. Is there a tool for compressing the springs and what is it called. It looks like the keepers that hold the valve are just held in place by the pressure of the spring . Is this correct is there any specific proceedure that needs to be followed