Air filter? I don't think so. If the air cleaner is clogged, shouldn't the bike run richer? Sounds like it's running lean. The carb is suspect, probably the idle jets. They are like the diameter of a human hair. One or all may be clogged.
Take the carbs off, and take off the float covers. Take out and clean the idle jets and main jets. Spray carb cleaner through them and all the other passages in the throat. Take off the floats (don't mix the parts) and check the inlet needles for wear. If your carbs are CV, check how the piston goes up and down. You may have to take off the vacuum chamber cover and clean each piston so it moves smoothly. Use vaseline to hold the diaphram in the groove (it sounds weird, but if yours has it you will know what I mean). Adjust the floats to specs, tighten the screws and install.