I'd love to, but I've been trying for a couple of years to figure out a way to accept an invitation to spend a couple of months in New Zealand, building two engines- - - -one for a 1925 Dodge 1 1/2-ton truck, and one for a race-prepared Toyota Supra!

The symptoms you're describing tell me the carb is running way too lean and adding the air cleaner causes enough intake restriction to richen it up. Try adjusting the idle mixture to run right with the air cleaner installed, then put LP down the carb throat when it's removed to see if the idle smooths out that way. If so, you need a less-restrictive air filter!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!