The E20 gunk that we see in our throttle bodies is'nt a pretty sight at all. I have also observed a lower mileage in my ride. Worst part is even premium fuels like Shell have 15% Ethanol blend!!.
The things is, 350 is too low a datum for a GST slab. Let it be higher, say, 700-800cc.. Makes sense that way when considering 'luxury' (in terms of the price that one is willing to pay)