most people dont like tuning carb'd engines, but i do! lol your not alone.
The Jets are what need drilling correctly (also known as needles, this is the case with most carbs, even a twin choke single weber)
Twin 40's are not too big for your engine, they just need to be jetted correctly, and set up properly on a rolling road. i know someone who ran twin 40's on his 1.3 mk2 jetta and that was awesome fun ! its all in the setup. problem is finding someone good to set everything up. injection engines are easy to tune, you plug em into a laptop an job done, due to that, a lot of tuners got lazy and so most now dont remember( or ever known0 how to tune a carb engine properly!
your local to me, and quite a few people i know round here have given me good reports on a few local specialists, so if you do go for it lemme know and i can send you in right direction!
for your engine, the easiest and cheapest route to better power is to fit a weber 32/34 dmtl carb, and a GTI head, cam, distributor, ex manifold and downpipe. get the weber set properly and that will take you to just shy of 100bhp easily, and the dreaded pierburg issues you no doubt have will be gone forever!
drop me a pm if you need any advice or help etc on tuning that engine, been there done that! mk2's are my thing and have my fair share of fun with em, any part you need i can generally get quickly and at decent prices too lol