The only genuine "Motorsport" E34 5 series cars are the M5 which have the WBS VIN prefix. The Canadian only M540i and US only 540iSport are also considered to be Motorsport models but as far as I know do not carry the WBS prefix.
Some markets got a Sport version of the 525i and 535i, which had a M-tech body kit, suspension, LSD, sports seats, metric wheels etc. I don't think these can really be considered Motorsport versions as such.
If yours is a 535i then it most likely is a Sport, sport seats and the M5 body kit are the most obvious give away, does it have these??
post some pics if you can, always keen to see E34s, M5s or not