Do you own / can borrow a temp gun or IR camera to check ex. pipe temperature after making a ride to see which side id hotter ? Inspect both spark plugs and diagnose them . As a natter of fact , replace the spark plug on the bad side to see what happens . I would hate to go through all this to find this out !
If the spark plug is good , then go to town diagnosing . I the bad side shows a lean condition , make sure everything is buttoned up around the throttle bodies , intake . etc . If all this is good , I would suspect the injectors . There should be an injector service in your area . They can verify or clean your injectors to match flow . Good luck !