Last 2 mos I have had P0369, fix was camshaft sensor within 1wk P1345, 1346, fix was replaced fouled spark plug. Next P0451, fix was downstream O2 sensor. Now 2 days later P0491!!!! I am trying to get this car thru emissions and it's one thing after another😡 I have checked SAP, Chk valve, hoses and solenoid switch. I can't fix this one. Suggestions?