Stock HEI setups are notoriously weak. They are better than the 60's ignitions(except the transistorized ignition) but they were only created to allow the motors to run bigger gaps and leaner carb mixtures so they would pass new emissions tests. Then GM stuck with the carb style HEI setup on it's trucks for years even though they were EFI. The Grand National ignition and LS1 ignitions are awesome, but the HEI is very weak. The examples I gave above of my own vehicles is pretty solid proof a strong ignition will clean out buildup. I've never had the top end of a vehicle cleaned or had it run through injector service. So either someone snuck into my garage and poured top end cleaner into my engine while I was sleeping, or the hotter ignitions helped clean out the chambers. Obviously a hot ignition won't clean off valve deposits but it will keep the back side of the valves clean. He's looking for ways to increase gas mileage and a better ignition system is probably the best bang for the buck. Tonneau cover, properly inflated tires, free flowing exhaust, free flowing intake, bigger plug gap with hotter ignition. Oh, and don't forget the Z-Max engine treatment with Linkite and the Tornado!
