I got 1970 cutlass 350 and out of no were it started weird idle changed the spark plugs and wires still did the same so I went around pulling plug wires to see the change in idle. When I came to the passenger side the two middle plugs made no change in idle. Also on the passenger side you can hear the difference in the tailpipes pulled the intake manifold off and found this

Does it look like 1 of my valves mite be stuck open

 

Possibly, usually bad things happen if they stick open. Has any work been done to the motor?

 

No no work has been done

 

Are you saying that to your knowledge that motor has never had a valve job?

 

It looks to me that your intake manifold gasket has been leaking. Did you run a compression test on the engine?

 

It looks like your gasket failed at the exhaust crossover port.

 

Never had a valve job and also replaced the valley pan gasket and did a compression test my numbers were around 120-125. After putting it back together no change still doin the same rough idle

 

Has the timing chain/gears been changed? Have you checked for vacuum leaks?