Test drove the bike on the flats seemed to have a enough power to hall my large body around. I found that it lacks power when climbing up grades. Wide Open to stay up to speed.
Forgive me if you've already tried this, but when you're climbing a grade and you need full throttle to maintain speed, that's when you downshift. It'll make more noise, but you should be able to accelerate.
If that's not enough, your bike might be running a bit rich. I fly into Seeley Lake in the summer and if I recall correctly, you're at about 4,500 ft. If the bike is jetted for flatland elevations, then you'll be running too rich, particularly in the summer when the warmer air is even less dense. A common fix for high altitude bikes is to rejet for a leaner mixture. This is actually the opposite of what the jet kit that comes with the aftermarket pipe does.
If you're on a tight budget, an aftermarket pipe and jet kit will not give you that much bang for your buck on that engine. You get a lot more noise, but only a few more horses near the top of the power band.
That 600, when properly jetted, should make enough horsepower to get you over the hills. I'd check with a local mechanic (who should be familiar with the altitude problem) and see about swapping out the stock jets for some leaner ones.