[roostafish]

I think you're going the right direction, but I'd try the less expensive things before going to the pipe. Cheapest way to get what you want would be to do the $75 RB Designs head mod. I realize it's half a world away, but if you have a period of the year where you have down time, I'd consider it. This combined with jetting will yield the most cost effective results. The LTR powervalve cover, or anything like it is also a worth while mod. It improves the low end response, is relatively inexpensive, and very easy to install.

A flywheel is a really good idea for what you are describing. I'd say get the biggest one they make. If there's a 16 oz available, get it. It's truly amazing the effect a flywheel has for keeping an engine chugging. A 16 oz flywheel will make it almost impossible to stall, and actually improve traction over difficult terrain.

All of these mods are inexpensive, and effective. If you really want a new expansion chamber, then that's one thing, but if you're after low rpm performance, one or a combination of the items listed above should make you pretty happy. The easiest two would be the flywheel weight and the powervalve cover, I'd do them both first and see where that takes you.