so it would be better to locate one with a bigger engine already fitted, as for the tuning I would not want to over tune the engine just something simple, or it would ruin the feel of the car as far as I'm concerned.
By chance are there any other engines such as a 1.0 liter engine that can fit the car cause I saw one for sale and the bloke selling it said it was standard, from the research I have done there are only 3 engines that were fitted on the 126 a 594cc, 652cc, and 704cc. I suspected it was fitted after but have no idea what it was taken from