trust me, factory fuel pump wiring sucks. At least from a performance stand point.

the amount of current able to be drawn thru a small wire is minimal compared to a fine, multistranded large cable. The electrons actually ride on teh SURFACE of the wire... so the more strands you have, the more surface area, and the more electron flux the wire can handle. a single solid wire that is the same size as 12 AWG will not handle as much current as a Finely, mulitistranded wire of the same guage. soo... the more strands, the more thickness, the more current capability.

stock 14ga wire w/ relays and resistors is not something i would try to wire a "High performance" fuel pump to.

hope that helps...

this would also explain why your aeromotive external was able to feed the 550's and keep you from leaning out after you hooked up another power source.