I work 16 miles from home. My BIS is standard apart from no airbox (previous owner installed a pancake filter really badly, it wasn't air tight at the base plate and the retaining bolt damaged the top of the carb) and I believe it may have bigger jets. I still manage to overtake several cars most days. Admittedly it needs lots of forward planning but the sense of acheivement is amazing!! I have no desire to modify mine to any great extent. I may one day buy a near death aircooled to alter.
I have had fast cars (ex police 24v senator further tuned by drug runners, caught by police helicopter, searched thoroughly, put back together badly, I bought it at auction for £50, had a displayed 170mph out of it!!) and I have built fast cars (mk2 polo, lightened with a tuned golf 1300 on the 1000 polo box, 1600 sierra carb, rolled arches, big rubber, nothing could touch it in the mountains) but not one of them put as big a smile on my face as the 126. I have had near 50 vehicles of all types from the 126 to a 1965 bedford coach and a winnebago.
A 126 is the wrong car if you want power unless you have deep pockets and serious skills.
Hardly any succesful engine swaps have been done so we really don't know what is the best engine to use.
If you have the skills get yourself to a breakers yard with a tape measure, if you don't have the skills but have the deep pockets, take it to someone and get them to do it.
Marc