Help! fuel pump or electrical

[4jrfox]

Hello, I have a 74 Bronco with a wire management form Ford Racing (I think it was 85 mustang wire set up.) Im running a gt40p 5.0 1997 Explorer engine and have had good sucess for 2 years. Im having a problem now that Im wondering if I could get some ideas how to fix / trouble shoot. This problem for me is WEIRD! When first starting cold or hot it will not start. Than I tap the fuel shut off to the off position and it starts right up. While it it running I depress the fuel shut off switch to the on poisition and it will remain running fine, If I dont depress the shut off switch while running it will shut off or stop running, I assume it's running out of gas . Now I will say that an electrical shop has messed with it in the spring of this year and the engine has been apart 3x this year. Everythings great (running now seamilgly great 45 minutes first time start this year). I thought it might be the fuel shut off switch malfunction, I replaced it with a new one same symption occurs. While the engine running with perfect 38 pounds fuel pressure, 50 pounds oil pressure. Any ideas?
Has any one ever heard of this happening?
Thanks, JOhn
4jrfox@sbcglogal.net