Hey mate. The CA20E or KA24E powered U12's are an excellent first car, good on fuel and generally unpopular which is a double edged sword
The KA24E's benefit nicely from intake/exhaust mods and an antrx chip. Be wary of KA24E 'extractors' as they have been proven to be quite shitty!! I believe the generally consensus was a 2.5 exhaust gave the most benefit, teamed with a decent muffler to keep noise down, or not
Coupled with a 3" intake tract, smooth stainless or aluminum to a pod being fed COLD AIR not warm engine bay air.
All they really need at the lower end of the scale is to breathe better and then be tweaked when it comes to fuel/air mixtures. Noss makes these chips and been perfecting them over many years.
Add a more aggressive camshaft and a chip tuned for it, you'll open up even more go.
eg: A mates U12 TRX, with a shitty 2.25 exhaust, extractors a pod, R4 antrx camshaft and antrx chip to suit made 88.1fwkw at a dyno day we held a while ago... where SR20DE powered N14 and N15 pulsars of varying levels of tune/work were making between 80fwkw and 92fwkw. However, I doubt they were making anywhere near the torque that the KA24E truck motor was making @ 2000-3000rpm!