Chainsaw Repair

A friend of mine gave me an ms280 and it looks like almost new - original bar and chain.  Anyways, he said it started acting up when cutting through a log, losing power in the cut.  He took to dealer he bought it from several years ago, could not fix or tell him what was wrong.  He fiddled with and gave up.  Long story short, he knows I like to fool with saws so I have it now and found that it's an IEM model with only the L and LA adjustments on the carb AND looks like the IEM is missing.  So far, can't find a replacement IEM from dealer.  Found the part # but dealer says its no longer available.  My question is, anyone ever replace the carb on one of these saws with a regular carb instead of the IEM model?  Thanks!