road.cc weighed a 50/34, 11-32 Tiagra groupset:
Chainset - 910g
Cassette - 355g
Bottom bracket - 90g
Calliper brake (rear) - 179g
Calliper brake (front) - 181g
Rear derailleur - 277g
Front derailleur - 106g
Levers - 486g
That all adds up to 2,584g, although cables will add another 200g or so.
I haven't seen an article toting up a Sora groupset.