The old fashioned way of gaining better performance from an underpowered engine are:
1) Reduce vehicle weight - remove everything you don't need and that includes body kits which just add weight and drag and do F all for performance.
2) fit skinny tyres, say 165's, as they have far less rolling resistance than wider tyres and will give improved top speed and mpg.
3) fitting smaller diameter tyres/wheels gives improved acceleration (but lower top speed)
4) Improve aerodynamics
5) don't choose A/C, even if not used it still adds weight.
6) Turn all electrics off, don't drive with lights on unless absolutely needed and turn stereo off. Electric devices consume power that draws current from alternator which makes engine work harder to generate that current. Having all the lights on, stereo, heater etc can use the equivalent of 5hp!
7) Use thinner oil. Not recommended but if you go to synthetic instead of semi synth you can normally go for a thinner grade which frees up engine power especially when cold and improves mpg. Eg. I swapped my old pickup truck from 10w/40 mineral to 5w/30 semi synth.
These are things we used to do 30 years ago to maximise performance of smaller engined cars. You may laugh but they did have some affect. Of course it is alot of hassle for minimal gain. These days huge gains can be made on turbo cars with remaps but sadly there is no so much that can be done with normally aspirated engines unless you spend big bucks on performance hardware.