KimberKenobi wrote:B) the additives in the V-Power cleaning gunk out of the system (if you usually use tier 3 or econogas)
My thoughts exactly. V-power has an excellent detergent. That may be the reason behind your improvement (if it wasn't the aforementioned placebo effect).
Assuming it was indeed the detergents that helped, you can save yourself a lot of money there by stepping back down to regular and tipping a bottle of Techron or Lucas injector cleaner in every few fillups.
And speaking of Techron, that's another great alternative. Regular-grade Chevron and Texaco gas has Techron, which is an exceptional detergent. No need to step up to premium when the car doesn't need it.