You're very likely right, I've got similar stories I could share. Ethanol in gasoline has made the problem worse. An easy test is to find some non-ethanol premium and give it a go. One common bit of advise is to install a Phenolic carb spacer, personally I've never had much success or seen much improvement from adding one. Luckily I do have a convenient service station that sells non ethanol premium, the only sure cure I've found.
Good Luck, Ron
