[Daox]

I just searched the thread real quick and only one person mentioned head work, and he said to port it which is a big no no for low end torque. I suggest reworking the head and combustion chamber to increase swirl and decrease hot spots and thus detonation. You can then shave the head farther than normal increasing your compression. Intake port work can be done to create a variable boundry layer increasing low end torque at the expense of little high end torque. Also look into adjusting cam timing to tinker with the powerband to keep it matched closer to your gearing.

I'd look into indexing your spark plugs as well.

Possibly look into fuel heating. This works on some engines, hurts others.