Riddle Me This...

[CapeX5]

Have been monitoring my fuel trims since replacing the motor on my X. Bank 1 has been 7-14, Bank 2 was always around 4-7. Wanted to get them closer to 0 and was going to have injectors cleaned or replaced. But, in the quest to resolve and engine surge on acceleration, I was told that the fuel filter should solve the issue. I finally replaced it 2 days ago. A pain in the ass by the way. But, done, surge better, but still there, but my trims have changed dramatically! Bank 1 from 1-3 and bank 2 is -.8 to -1.3. Was the filter that dirty that it was restricting flow?? I am actually going to cut open the old one today and investigate. Will post results and hopefully pictures. I don't know when it was last changed but it did have a BMW logo on it. Would be interested in hearing your theories on what might have been causing this.