I have a 2005 Z4, 12,457 miles on it. I had the 1st fuel pump replaced at 450 miles, had the same problem while at BMW homecoming 2 times, had it back to the dealer 6 times. BMW reps at Homecoming said they would get in touch with my dealer, that never happened. Each time I took it to have it fixed, the noise went away by time I drove 80 miles to the dealer. SO, the last time it made the loud noise I called the dealer to have someone come to my home to actually hear it, which he did. I HAD to drive it to the dealer for them to replace it again (2nd time replaced). Well here it is, I put 400 miles on it and the NOISE is back. Nice sunny day & can't drive it. I'm so fed up with this car and BMW. I thought while it's under warranty they are supposed to flat bed it & bring a loaner??? NOPE, I had to drive it back & forth, 80 miles, 2 days off work. I see that the 03-04 Z's had recalls out. I can't enjoy this car, I always wonder if it's going to stall on the highway. Thanks for letting me vent. I would like to hear from others with this problem.