My buddy's max has a 503 duel carb. He lost the mid-range idle but full throttle seem to be fine, what would you guys advise to start looking for?

Thank you in advance,

Roger

Roger,
Can you provide more details about the issue with the engine? What rpm are you referring to when you say mid range idle? Does it happen in flight, on the ground or both? Does it try to quit, run ragged/miss? Any ideas what the egt's are when it happens? Did the problem come on gradually or suddenly? Anything you can add might give the us some ideas.
Dick  

More info this weekend I wasn't in the cockpit I did pull the plugs the two front ones were light brown rear was wet going to start on rear barb.

And yes it started all ay once, one weekend running fine next weekend problems,