I can't speak to whether the higher octane will make your Audi perform better. You'll have to do your own analysis.
You have to read up on how this Top Tier gas got started. After 9/11 and subsequent hurricanes, refineries were cutting corners on gas production and some of the car manufacturers were seeing fuel related issues so they started this consortium of Top Tier gas manufacturers. the idea behind Top Tier gas is these gas providers have a certain level of cleaning detergents in ALL OCTANE LEVELS. This is why such brands as Amoco and Exxon are not part of this group. Over the past few years, refineries have tightened up which is probably a case of the "industry regulating itself".
Top teir gas is a marketing tool for the gas manaufactures that use over and above the detergents required by the EPA. The fact that Mercedes, Ford, Volvo, Chrysler, etc are missing from this consortium tells yo tha not everyone is buying into this.
The big question isn't do these gas manaufacturers have more detergents than regular gas stations, the questions are what level does your car need and does the EPA minimum meet that requirement? Does Shell/Texaco have more detergents in their gas than Rutters'? Yes. The big question is, "does it matter?" I think since this consortium was started by a handful of auto manuafcturers and has not been adopted across the industry speaks volumes. Also some very big gas producers are not on that list like BP and Exxon/Mobil.
I live in York, PA and we have literally no Shell stations and maybe a
handful of Top teir gas stations in my area (Snoco and a couple of Texaco stations). Our gas is dominated by
Sheetz, Rutters, Tom's, etc. and we have BMW, Honda, Audi
dealerships. So technically these companies should not sell cars in my
area since we do not have the gas stations to support them.
if you have a Shell station and want to use that gas, by all means do. But I wouldn't go out of my way or pay extra.