The only other thing offhand that is common that can cause this issue is a PCV/crankcase circulation issues. All those vapors from the crankcase (by product largely of oil there) get into the combustion and can screw up the octane (bring it down). That is another reason I have been a stickler on oil for a long time. However, I worry less since I disconnected my hoses there off the PCV valve.

However, with the tank, there is muck that can get in there. Here in Florida, we have ethanol and that can separate in the ank over time. Well, in Mexico, the gas wasn't the cleanest and I had issues with it.

Thus over time, the only other common denominator besides PCV, dirty injectors, dirty air filter is a dirty tank.

This cleaner seems to pick up and clean out garbage that the other cleaners mentioned just don't do from my experience.