I have a friend who has a 88 535is that ran out of fuel and fried the pump. He replaced both pumps, filters, pressure regulator, coolant temp switch, and main relay. His fuel pump relay is working fine. Car continues to not start, it turns over and will back fire on letting go of key. Car ran well before this, so not sure of bad sensors. The only problem he had was a occasional hiccup at freeway speeds. Any suggestions?

2001 330i w/ m and sport package