Dude, before spending any more time and money go buy the fuel system cleaner and fill up with the best gas you can buy (93)
...then go run that car down some back roads like you stole it.
Rev it up hard, have fun. And remember, fuel sys cleaner ain't gonna do the work in 5 mins.
It might take a good half a tank to clean up the gunk but you will notice the difference once the stuff is out of the system. I use Techron every few tanks of gas and love it.
I hope I am not messing anything up. If so, please someone tell me....I don't drive the car but once a week, sometimes less than that. 2003 2.5 with 75K.
2003 Z4 2.5i Silver/Black