Why does your friend think it's an injector? Doesn't sound likely to me.
Sounds much more like a vac leak to me. Check the vacuum lines for holes/cracks. The major ones are:
Intake boot to ICV
IVC to intake manifold
Crankcase vent to Intake boot
Crankcase vent to ICV (small hose)
Bottom of intake manifold to Fuel pressure regulator (small and hard to find)
At least, those are the ones on a 325. If anybody knows of them being different on OBD2, please correct me. Either way, just try to find a leak. Might help to use starting fluid. Spray starting fluid or carb cleaner at vacuum lines while the car is running. If the idle changes, then some of the fluid has been sucked up there due to a leak.