I tear the trails up on my kx250 So I know its doable.
Huge difference between power spreads between the 250 and the 80 (but you know that). Just because they are both motocrossers doesn't mean they are comparible beyond that point.
There isn't too much that can be done to make the little 80 have low end. You can improve it some, but it will still be weak.
A FMF SST pipe or Pro Circuit pipe are both designed to help a little in the low to mid range power. You could also add a torque ring to effectively lengthen the headpipe, which would shift the power band down a few hundred rpm in the rev range. It might come on 200 rpm sooner, but it will run out of juice 200 rpm sooner as well.
Since it's a trail bike you need a spark arrestor, so throw a FMF Turbine Core II or Pro Circuit Type 296 silencer on there as well. I don't know if either will really help low end power, but they keep you legal, which matters.
FMF also makes torque reeds that should help with low end a little bit. A reed spacer helps some bikes with low-mid power by adding volume to the crankcase. I don't know if anyone makes one for that bike, or if it would even help.
Lets not forget about a flywheel weight. Stealthy makes a 10 oz for that bike. It won't add any power, but it will smooth out what's there, plus make the bike harder to stall out. A flywheel weight gives the "feel" of more low end power.
After that it's engine work. Cutting the base of the cylinder down will lower the ports and shift the power band down in the rpm range. Like the longer head pipe you'll gain down low and lose up top. Cutting the cylinder will require the head be cut/shaped to keep the squish band and compression in check. Since you are in Colorado and at a fairly high altitude (I assume) you can actually run higher compression without detonation. This is a good thing, because higher compression means more low end power potential.
Even with all the above mods the 80 won't have any real "low" end to speak of. But the power will be shifted into a much more usable range.