The amount of detergents in the gasoline does make a difference. I do not have the Brochure BMW printed and I picked up at one dealer anymore, but it had a recommendation about the frequency of use of injector cleaner, and if I remember, it was fairly frequent when not using fuel from the TopTierGas group. I'm just curious if following that guideline would have made a difference. I occasionally use a tank from a place that's not on the list, but that's probably less than 5% of my fillups, and then, they're usually not in succession.
I drove both the V8 and the I6, and while there was more power, for most of my driving, I find the I6 has plenty. Now, I would have opted for the diesel, if it was available I think. That extra torque and mileage would have made a difference overall.