The installer used the same AWG wire as the EMPEG supplied. I believe that it is 16 gauge. I don't have a voltmeter to test both locations, but it sounds like not even one person has been able to remove the engine whine from their BMW.
I don't know what the bonnet and braided strap are. Could you please clarify... And I don't know what ignition leads where used either. Sorry that I have no better answer's for you, but I do know the the RCA's that were used are not very thick and insulated. But from what others have said, even using the triple insulated RCA's, moving away from the power/gnd leads still didn't make that much difference.
I read another post that said that the way that a fellow BMW owner fixed his problem, was to use the grounded RCA's and ground it to the sled of the EMPEG. Does that sound like a good Idea?