i've come across a few cars that the fuel pump has gotten real weak and is only mantaining 20 odd psi, if it's running smooth look for common shared systems, had a 95 740il with one plugged cat and a blown pcv plate that was a pisser to figure out, it wouldn't get out of it's own way the computer was trimming the mixture 50% lean on one bank and 50% rich on the other among other weird readings (damn i am getting to hate the later cars, they get pissed off and then over correct and snowball) the early cars are easyer to figure out when things get weird
all america wants is cold beer warm cat and a place to take a poop with a door on it