Is it the 22r or 22re? Carb or Fuel Injected?
Sounds very much like a vacuum leak or a timing issue. Also how many miles are on it? These engines need to have the timing tensioners and idlers changed around 180K or so. Especially if you donÆt run a OEM oil filter with the check valve in it causes premature ware on the tensioners.

On one 22re I had the tensioner fail and the chain wore a hole through the side of the housing. It ran pretty crappy for a while befoe the guy boght it over for me to look at.

Something maybe to have him check.