maybe the fuel pump charged you for 14.5 and you rode away with 13.5 ?

Sounds normal to me, however after 10 years and many km's on the bike, you know the bike best.

If it is something else, i would guess at something is partially blocked somewhere, either tank, lines or carbs. or the vacum hose is restricted slightly.

Pretty sure I found the issue today. The tap to carbs fuel pipe which has been replaced in the past due to the old one getting ropey was a little oversized, and when I took the tank off today while refitting the rear subframe I noticed it had a pretty good kink in it. Since my spare carbs had a proper sized pipe, I swapped it out, so hopefully that solves that one.