Re:Higher RPM upgrades?

Yes, I see what you're saying, a ported head is something my mechanic hinted at when talking about making more power, and I was also thinking about a set of cams, and these mods would be fitting because I plan on using the little Jimny as a rally car, not as a normal offroader.
also, I'd prefer to keep the engine vvt-less as to keep the head as mechanically simple as I can, not caring about the economy and power advantages.
I'm still a little confused about my engine's powerband, I think the mods I did shifted it in some way, and I need to study it a little more before I can make adjustments accordingly

You might want to check this out about a Jimny prepared by Dave Marsh Racing

www.superproeurope.com/news.read.cfm?articleid=61

and this one top gear.

www.topgear.com/car-news/the-great-outdo...y-go-desert-rallying

Yes, I saw that article and it is pretty interesting, and also goes to show that the little Jimny can become a rally car with some minor mods, which is something I like very much

As one of the very small minority of Jimny drivers with actual seat time circuit racing a Jimny I think you are looking in the wrong place for gains. The m13 is a very entertaining engine and is good at making you think all sorts of performance is happening because it's so free and quick to get up the rev range but in reality it is mostly just noise. That is not to say you can't make an m13 Jimny relatively quick but that is done by working to conserve momentum. Inn other words once you get it moving don't let it slow down. This is achieved by having very controlled suspension and effective management of the heat generated by the brake system. On Dreadnaught, my last Jimny, I had big bore sports dampers from trailmaster, custom lower stiffer road springs and ebc brake components and 5.1 fluid and relatively sticky road tyres. Add all that to loads of seat time enough to be totally comfortable with how the car would react and I was not only able to hang with faster cars but embarrass a few along the way.

Oh, absolutely, I use that style of driving too when I'm on tarmac, keep momentum and brake only the necessary, if at all.
I have upgraded my dampers a week ago, and I have to say, the car feels a lot more planted now, at least on the road, I still have to test it off-road, since my dampers should shine there.
Talking about the brakes though, I was driving today and decided to push a fair bit, just to have some fun, and after a while, I noticed that the brake pedal felt strange, it was like it had two "steps" (?), it was soft for a little bit of travel, which is normal for my car, then harder like if it had actually began biting, but with not that much braking happening, and then soft again for a little bit before actually getting harder and starting to brake effectively.
The thing is, I almost hadn't braked before that, but I pushed the engine a lot, and passed on some little rocks and animal residue on the way, could it be that my brakes are on their way out? Which is probable since my disks are not thick at all, or could the gunk be causing those problems?

Also I was thinking about my exhaust, I read around the forum that these engines really love getting a better flowing intake and exhaust, and a few months back I got a sportier muffler to replace my rusted stock one, I was thinking about taking off my cat and straight piping that part of the system, would there be any way to do that without having to retune the car because of the sensor?

The post CAT sensor doesn’t normally change the mixture, it’s just there to check that the CAT is working and shows a fault if it doesn’t get a good reading.

The pre-CAT sensor on the other hand does fine tune the mixture, in conjunction with the Mass Air Flow sensor.

So usually you can just disconnect the post CAT sensor, or perhaps put a bypass plug in.