In the service you might want to see about taking it for an intake cleaning, injector cleaning and some fuel additive. BG makes the best stuff, take it to a shop that does it (has it). The fuel additive should go in on a full tank, fill the tank back up when it gets to half, then run like you normally would. The results may not be immediately apparent but I did it to mine when the the BG guy was in demo-ing it for our shop. My 5 runs like a champ (94 with the M50tu engine). It was good to start with but better then ever after.
Also, BMW's of that era aren't necessarily tire shredders off the line (yes, there are those that do it), they're more built to do 155 on the autoban all day long without breaking a sweat.
One other thing, when you replace stuff. Stick with OEM and NEVER go anywhere near DDM. That is unless you like crashing into stuff when you HID's fail and your lowered struts collapse.