I would stay away from pump gas on an RS. It wasn't mean to run on that low of an octane, and you will be creating so much carbon build up, your rebuilds will take twice as long as you clean the flapper valves, exhaust ports, and chambers of the crap.

Could you clarify why there would be more carbon build up? As I understood it Av Gas (or blue gas) is merely regular pump gas without the extra benzine added but with a whole bunch of Tetra-ethyl lead added (around 4~5%).

As the carbon in build up comes from the fuel/oil mix, if you are not putting in extra oil and are running the same AFR the amount of carbon in the exhaust will be the same to all intents and purposes.

I believe that the combustion temeprature is roughly the same between the two types of fuel (the calorific value is about the same), the extra power in the Av Gas comes from the fact that lead is a better knock supressor than benzine so the engine can run at a higher CR which helps deliver more of the combustion heat to the crankshaft.

Cheers