OK, these modifications are probably quite obvious for most of you, but I thought I should fill in anyway...
The best way to get more low grunt "carb-wise" is to actually get the "best" air-fuel-mixture, with the best pressure balance. An other thing that can help the low end grunt is to make sure the valves are not tight, as that can kill performance on the low RPM-range.
An other thing, which probably will have a huge effect, is to re-grind the camshafts, for a shorter duration, but that will result in lower horse powers, mostly due to the fact that max torque will be recieved in the lower RPM range.
No, I have not done anything with the camshafts, but if any, I would change to ones with longer duration (read GPZ 500), mostly due to the fact that it will increase the peak horse power.