well ... that funny guy was pulled over by puhlice because they thought that the car was stollen when he put his 520d badge on it .... I read the storry on the m5board.com
what I think though .... very few people know what m5 is or what 525 stand for so debadging or underbadging would make little difference. some people who know what m5 is have NO CLUE how fast it is. they think they can dust a large 5 series BMW in their Golf GTI. but ...for me if I owned an m5 my heart would miss a beat every time I'd walk up to it and look at the M5 badge and thought I #$%^& own and drive this beautifull machine ....
I'd leave it where it belongs
by the way, a funny storry happened when I first got my 540 and took 4 other guys from the office for a ride ... one of them owned a modded Mustang Cobra ... well ... 5 of us went in and I took them arround the block in 1st and 2nd gear. you had to see their faces!!! especially the 'stang owner ... he never thought that a large luxury sedan can be so fast and agile. He wanted a 540 ever since
F10 535xi M-Sport, Dark Graphite
E39 540i Sport Titanium Silver - SOLD
E34 520 Black - SOLD