i have found that most modern engines if serviced and not over heated seam to hold the power outputs quite well,
m50 m52 m54 m60 m62 types etc
i had a 92 325i with 200k's make same power as a 96 328i with 100k's on a dyno
and as above 161kw witha 540i is bang on.
no so much with m20 and m30 engines, (maybe valves no sealing as well) and old afm's going off etc