[BMW Atlanta]

Pinched or plugged would be the immediate assumption. Both lines from the tank should be vented to atmosphere now, so reversing them is out of the question. Hard to say for sure without seeing every step as it was taken. Dont know if it would even run with the fuel lines reversed,.....never tried. But I imagine that pressure could still make it to the fuel injectors as the check valve is in the tank. I would reinspect every step to the ground wire at the motronic to lines or fitment of exhaust gaskets.