It's funny how many of us bought into the idea that the aftermarket silicone IC boots were better. I've tried them too, only to go back to the OEM.
ALTA Red IC boots *The one exception to Red makes everything faster. Under load the leak and you loose boots. Had them, installed them, had a problem, put them in the trash, OEM rubber boots ever since, no problems. End result: They ALTA work but don't, just like everything else ALTA. :devil:
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...