We had a 170 TDi Golf GT Sport and in our 2007 version there was no boost gauge, if that helps.
Plus at that time the 170's had the twin GTi style exhaust, whereas I think the 140's at that time didn't.
Specs may have changed through time I guess though.
That said a look inside the service book inside cover will show the little KW sticker, whatever 170PS translates to in KW.