my point is that the chainstay bridge is a mass-produced bit, so nothing in this case that would provide a clue to the frame brand.
However, from your persistence I had to go to VeloBase and comb through all the late '80s early '90s Peugeot catalogs ...you are right: there ARE some similarities to the top-of-line models, but I don't see one (yet) that has all the features of Neto's in one example.
Still I have to eat a little crow and give props to Chombi, here I thought you were just being a rabid Francophile, again.
The one detail I don't see in any of the "good" Pugs from this era is one that would have 27.2 seat post (531 or Columbus steel) and with the internal TT cable routing, all I see have external brake cable running under or on top of the TT.

What about the serial number: any correlation to Peugeots (location on BB and system) in this 80s/90s timeframe?