MY BLAZER SOUNDS LIKE ITS GOT SOME SPARK KNOCK TO IT, I USED HIGHER OCTANE GAS, FUEL SYSTEM TREATMENT BUT NOTHINGS WORKED, AT FIRST I COULD ONLY HERE AT LOW SPPEEDS BUT NOW I HEAR A LITTLE BIT AT HIGHER SPEEDS, IT SOUNDS LIKE ITS COMING FROM THE BOTTOM RIGHT SIDEOF THE ENGINE, ANYBODY KNOW WHAT IT MIGHT BE LET ME KNOW THANKS