You could also start a regimen of using some TC-W3 in your gasoline. That will lube your upper cylinder and clean it at the same time. It will burn off clean so you won't have deposits. Just start out reading the fuel additive section to get a feel for the right mix and add it to your gas at each fill up. I've been using it for almost 2 years, every fill up, Winter, Summer, Spring and Fall and have a smooth acceleration and no knocks from the Ethanol in the gasoline. It takes some time to find the right mix for your vehicle....less is better than more...in the case of TC-W3.
Good luck.