I can bet a few dollars you will not find anything.
On the other side, if you take out the injectors and have them serviced you might find a few of them might be getting clogged, or the fuel pattern is not what is supposed to be (the latter is normal, and for street driving you will not notice). They will clean them, change the filter & O-rings and re-calibrate them. Clean thoroughly the "receptacle" of the injectors - if the O-rings were bad, you will have a lean situation and fine particles will be lodged there, where the O-ring should seal. You will have unmetered air going in right there. The only way to test is with some carb cleaner: start the car (with that engine beauty cover off), make sure the engine is cold when you do this - so first thing in the morning, and with the engine idling, spray sparsly carb cleaner around the fuel rail. If the rpm climb, you have bad injector O-rings (you have to be certain you don't spray around vacuum lines, because it will alter your "test").
Also, when you are here, and the if you remove the injectors, clean thoroughly the electrical contacs - these if slightly corroded, will give "misfires" every now and then.
Now move on the other side of the engine (from driver side to pass side), and inspect carefully the boots of the coils for each sparkplug. If you see any hairline cracks - time to change them. You can still drive the car until the replacement parts arrive.
A badly torn rubber boot might even not work on that plug, or maybe randomly.
Looking for a DIY? Parts? Check this out, it might be your ticket
TMS underdrive pullies - Stewart WP - PSS9 - Beisan Vanos seals - Zimmerman cross-drilled & Akebono Euro - Deka 649 MF - 55w HID headlights - 35w HID foglights - Hualigan double din - ACS (rep) alu pedals - Euro central storage console - Breyton Magic Racing staggered wheels - M5 bumper - M5 steering wheel - Tint
Stable: e39 M54, e53 N62 & Tribby