the oil temp is a big issue imho on the n54, with many peeps getting additional oil coolers. as with any engine warm oil is good hot oil is not. what constitutes warm and hot is engine specific. the n54 seems happy from 80-120 over 140 the ecu will pull power. there is a chart here somewhere with the heat and power reduction stages. for me in traffic i can see up to 120, on the track i have seen 130. the good thing with the jb4 is if you 'feel' things gettign a little hot simply turn on the max cool function and temps will drop pretty quick.
BTW congrats on the tune and enjoy