Tires and suspension come to taste and expectations of use. If you're taking it to the track you need full suspension, looks you can get away with springs etc. For power, Guru-Pete has let us know about a timing advancement that adds 3(IIRC), Injen's intake was tested on a versa running the same engine so... another 4, I'm sourcing a downtube back at 2-2.25" (to match the cup cars roughly) and hoping for another 3. Yeah it only adds up to about 10, but that's a 10% HP gain, which for the cost of fabing it yourself / knowing machinists - the most expensive part will be the intake, and will be noticeable.
As said it'll never be a "fast" car without serious money thrown at it, but for a lot less you can get it to go fast around corners. I put on the fully adjustable Tein coilovers and have 3 inch wider rims than stock (don't do this unless you're willing to do body work lol), without the front sway-bar reattached (this weekends job) I'm still throwing this thing around 30km/h curves at 90 with no squeal or understeer. Cheapest tire I could find / what's on it are hercules imove's, I'll be investing in a better quality tire next year since one of them has already warped...
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View my fuel log 2015 Micra SV automatic: 7.1 L/100 km ... 39.9 mpg (Imp) ... 14.1 km/L ... 33.3 mpg (US) ...