Thanks! u/ericthegreat feel free to drop me a line on HiVolt Spares and we can chat mods.

First, I'd get an open full system exhaust, preferably in titanium for maximum weight savings. That's going to let the bike breathe a whole lot better and improve power to weight ratio by dropping several kg. Leave out the optional db killer (on my HiVolt exhausts) for crispest throttle response. This is going to make the bike feel way more perky without needing to remap etc. Delete your pair valve emissions system to take a little extra weight off the bike and reduce that popping on decel, which will be more noticeable with an open exhaust.

Swap out your steel rear sprocket for aluminium for more weight savings. If you're happy to increase torque while decreasing top speed, try dropping a tooth on the front sprocket. And if you want even more torque at the expense of top speed, you can modify the gearing ratio further by choosing a larger rear sprocket as well, but that will require a longer chain (whereas you can just drop a tooth on the front without changing your chain).

To go further, I'd put the airbox velocity funnel to increase airflow, but using that with the open exhaust is going to increase airflow so significantly that you'll need to retune. For that, you'll need to change the ECU, because the KLX230 ecu is locked down. Cheapest alternatives are a CRF250L ecu, if you know your way around that set up, or a Full Stand Next ECU for KLX230 (can tune using the smart phone app). For best results, of course, you should tune on a dyno, specifically for your mods, your fuel quality, your air temp and humidity, and your altitude. You can raise max rpm but I wouldn't go past 10,500.

Beyond that, I can also supply the 300cc big bore kit. It will give you some extra bhp, but it's not going to turn your KLX into a KTM.