Stiffer springs than stock = better???

The diesel engine version of the Jimny have a thicker anti roll bar which will help you with cornering whilst preserving compliance for gravel surfaces.

The valve springs supplied as standard will be suitable for the maximum revs. that Suzuki have designed the engine to achieve and there is no point in exceeding them. The consequences of "going that little bit further" will be accelerated wear and , ultimately, catastrophic failure.

Roger

Most engines reach peak power before peak rpm. Power is limited by the problem of getting the fuel/air in and the exhaust out, so along with stronger con-rods, valve springs, high lift cams, etc you might also be looking at inlet and exhaust manifolds as well as a high flow air induction system, it's all going to start adding up.

Then the other problem is gears, most high reving engines have a narrow power band, that means more than 5 gears to keep the engine in the sweet spot.

Power and Torque of a Jimny
 
www.jimny-crew.com/jimny-on-the-dyno.html
 

The ARB quick disconnect sold by Jimnybits stiffens up the rollbar quite a bit.

If you don't do any off-roading so don't need the ability to decouple the ARB then I guess you could just cut the bar and weld a tube over a portion of it to get a similar effect without spending the £80.

...or like Lambert says, get an ARB off of a diesel.

ok so first thing to do would be get a diesel model ARB and see if that gets me the results i'm looking for.
i'll call the dealership near where i live and check if they have some 2018 or so diesel ARBs. i'm pretty ignorant on the subject so i'm gonna ask, does the jimny have only 1? or does it have a front and rear one like most vehicles (i suppose)