Hello. Multiple misfires. Started happening while in idol. Runs fine at 2000+ rpms. Replaced plugs. Tested coil packs, power plugs, fuel pressure good at the rail, cleaned maf, will not run at all with it disconnected. Seems to be an air/ fuel combo. Smells rich. When idoling it misfires and the engine shakes, wants to stall. Not sure what else to check. Codes pulled p0300, cylinder 4,5,6. Thanks for any help.