Maybe I missed that...getting old. Yes, I would use Techron first then use the Chevron gas to help keep them clean.
Back in the day, I was a Service Manager for a BMW dealer and we would use the walnut shells to clean the exhaust port in the head, but, everything had to come apart and a special machine would blast the chamber with the shells and vacuum it out at the same time. It is not for a "Harry home owner" to do. I wouldn't bother if it is running smooth.
There's my nickel. LOL