Brake Pedal Causing Engine to Quit

[Kabong]

Greetings,
I have just finished replacing the starter on my '80 FI pininfaria with one of those new fandangly gear reduction models. I got the car started up and running, but it appears I may have done it wrong or, more likely have a new problem. When I press the brake pedal, the engine dies. Engine RPM is insignificant as it dies at high or low rpm. The only thing different that ocurrs when I press the brake is the lights coming on. So I suspect on of two things;

1.) My fuel pump is on the outs and the extra draw from the lights causes the pump to slow resulting in a fuel starve.

2.) I have a short or ground issue that is triggered with the lights circuit being energized.

Have any of you guys found anthing odd in your repairs that could cause something like this? I know something is wrong back there, as my fuel guage flickers as well, but it has done that for several thousand miles without causing problems, other than me fogetting to spin the odometer when I fill up. Any help would be greatly appreciated.

Many thanks

[WYSpider]

Vacuum hose? Brake booster uses vacuum although I would think it might kill the engine only at low rpm.

[124JOE]

my car keeped staling it was the main ground connector "loose"