1996 Mystic Cobra 4.6L DOHC Has A P0300 Random Misfire

[wheelpro]

My Cobra has a P0300 code random misfire and a P1455 EVAP I've replaced spark plugs, EVAP purge Solenoid, fuel filter and it's still running bad. It went from running smooth to running with an extreme mis what's the chance that a bent valve is causing the problem? Or a dirty fuel tank or injectors? I'd appreciate any advice