Make sure when you press the pedal down the butterfly in the carb is all the way open. I know you had to rig the linkage for the new carb. Also check that both barrels are opening. I'm not familiar with the Weber but I assume it's manual linkage. Make sure the choke does not flutter, stays place when hot.

I'm still thinking fuel starvation or the vac advance on the dizzy is not working. When you timed the engine did you plug the vac advance?

98 Montero with cold weather package
96 Toyota Land Cruiser, fully locked Mall Machine :-)