as above, 2.0 16v is the best way to go, not a lot of power to be had from the 1.6 realistically. Yes people will tell you the Super1600 cars are based on the same engine with 220bhp but there's very little left over from the original engine. 172/182 engines are getting expensive now and the 140hp version from the laguna etc while being cheap, probably isnt worth the hassle of swapping over.
There is the turbo option which has been done quite a bit, Search on youtube for K4M turbo for some ideas. TWR performance im sure they were called from Portugal used to do a full kit.
Staying NA and 1.6 there is a few options for cheap ish gains albeit small ones.
Megane exhaust manifold with no cat (clio one has a cat)
F4R (138/140hp version) throttle body
Fastchip remap via RSTuner
exhaust/ filter - usual breathing mods
Few of us on here have played with K4M's before, have a search for Oliver_K4M he fitted one to a mk1 clio and done some power mods, There was a guy who built one on bike carbs if i remember right sure he was called Hutchie. Then there was Bloke who Turbo'ed one.
Mine is standard apart from the Megane manifold and in a light MK2 PH1 goes really well.
