The X17 ran via (from the City Centre), Great Western Road, Anniesland Cross, Bearsden/Switchback Road, Canniesburn Toll, Bearsden, Baljaffray & Faifley and used appropriately branded step-entrance Pointer Darts (in the same style as the 'Express Yourself' branding First used south of the border and ofc the Cumbernauld expresses at the time). It was later renumbered the 40D, then the 118 (I think) and finally the 6B in May 2013 when SimpliCITY came in. Was withdrawn in October 2015; it had been a peak-hours only service from it's days as the X17 through to it's last days as the 6B IIRC.
It may be the 217 you're thinking of as
@PaulMc7 notes.