Welcome to the forum Dave. I've been to your hometown a few times, but that was a long time ago.
Unfortunately, there are only so many budget-friendly things you can do to wring a little more power out of the 1980's-designed engine and, to my knowledge, there's really nothing you can do to wring out an appreciable amount more even if you spend some serious money doing so.
Sure, the HP can be upped, but at what cost?
I'm not an engine guy by any means, but it seems the design of the engine limits how much air and fuel you can move through it with optimum efficiency and unless you can find a way to add another cylinder, you're never going to approach the power generated by a modern twin-cylinder engine of the same displacement.
The KLR just is what it is. If you continue to find its performance completely lacking for your riding style, you might want to consider just finding another bike with more power.