Mark,
It is somewhat doubtful that the fuel pump wiring is causing your problem. If the connections are clean and tight, it doesn't matter all that much where the power comes from, as long as it's an ignition switched source. It is more common to wire it to the ignition-on hot side of the fuse box, but ultimately, all the power comes from the same place. You don't generally have to worry that you may be overtaxing the "local supply" of electricty unless the fuse and wire in the circuit can't handle the total power demand of everything connected to it.
More importantly, where was the pump mounted? and what pump did you use? Most auto parts store sourced pumps are no good for these cars, as the fuel pressure should not be above 31/2 pounds, whereas most auto parts store pumps are at about 7 to 12 pounds. This can account for poor starting and driving performance, as you are in a constant state of being too rich, or even flooding. Also, an electrical pump should be mounted down low on the chassis and as close to the tank as possible. BUT, keep it out of the trunk!. Let me know what's happening.
Motorbill
From Lola to Land Rover, If it's British and has wheels, it's likely I've bloodied me knuckles thereupon