i have codes p0303 & p0172 missfire #3 and rt bank to rich. new coil, plug, injector on #3. compression comparison #3 low 2&4 weak. dealer states cam phasers need replaced??? everything i have read is the cam phaser cause noise, but have not heard anything about compression? i guess it would make since as the phasers change timing intern opening and closing the valve at an incorrect time? anyone have this experience before??