** Guzman Y Gomez gains 5.4% to A$40.395; top gainer on S&P/ASX 200 index

** UBS upgrades to "neutral" from "sell"; raises PT to A$40 from A$37

** Says Mexican quick service restaurant chain's unexpected same-store sales growth (SSSg) and EBITDA margin rise may pleasantly surprise market

** Ups FY25/26/27 EPS estimates, citing higher Australian SSSg and EBITDA, surpassing prospectus and market consensus

** Adds menu innovation, broader daypart participation, delivery growth and increased opening hours key drivers for co

** Sees potential for net new store growth, with 15 opened in H1 of 2025; forecasts 31 for FY25

** Expects Australia and Asia-adjusted EBITDA/network sales to swell from 4.1% in FY23 to 6.9% in FY26; growth projected beyond FY26

** Stock rated "hold" on avg; median PT is A$39.57 – LSEG

** GYG gained ~35% in 2024 after debuting in late June

(Reporting by Kumar Tanishk in Bengaluru)

((Tanishk.Kumar@thomsonreuters.com;))