I do Dave. And after 3 smoke tests the car and boots show 0 leaks. I know people like to point the finger at these, and I don't disagree they were a nightmare to get on, and I gouged my first set pretty bad.
Bumping this thread. I also have the occasional P0171 code and a DT bypass valve on a 2003 R53 with ~190K miles. Car has a 15% pulley. In addition to P0171, it also also gets code P0234 for excessive boost.
Just like the original post, it happens when cruising on highway in 6th gear and when you put any load (like trying to accelerate without downshifting at 80+mph).
Have replaced fuel filter, fuel pump, post-cat O2 sensor. The car has stock IC boots which were checked and reseated. Next up, will replace the fuel pressure regulator line next weekend. Fingers crossed...
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