Bow many times is safe to seafoam??i did it yesterday 2 times with a half bottle each time and im still hearing a knockin sound when i turn my truck off.the seafoam cured the ping when driving.but when i kill the truck no matter if drove for 2 minutes or 2 hours theres a knocking sound(like someone tappin it with a hammer)comin from engine...any ideas on how to stop this???