I got a mini back fire coming from the intake, i got a 2003 ford f150 stx. with a 4.6. its got now 61000 miles on it, got a k&n cold air intake on it, and a magnaflow exhaust. hypertech programing, but just for the governor, i has cleaned my mass airflow sensor, cleaned the airfilter. it does it more on cool days, but also on warm days, when i get my foot off the gas pedal i can really hear it, what can i do to correct it with out having to take off the spark plugs and check the valves? any help , plzzzzzz