Well, another thing is that BMW manual recommends BP, but Top Tier Gas has no BP. If we need to put in injector cleaner so often ourselves, then BMW is way too sensitive. I recently read an article (I think on insideline) about a comparison between no name gas and brand name gas. After 10,000 miles, the difference in engines are minimal.
I really think it is as simple as BMW got a batch of defective injectors.
MJ14 535dx - Imperial Blue
MJ10 550 GT - Imperial Blue (retired)
MJ07 530i - Silver Grey (Sold)