If the ecu is cutting fuel, couldnt we power the fuel pump with a switch or something of that sort to bypass this?

Hit about 125 in my auto

 

I don't think anyone knows is going on at the point of the speed limit. The real way to do it would be to get on a dyno and log parameters ala UpRev, and see which one wigs out and at what speed.

Whether it be throttle, fuel (IPW), VSS/ABS feedback, or something in between

 

I don't think the ECU is cutting fuel but closing the throttle body enough to limit the speed. It isn't like a hard cut-off. Just hits 130 and stays there. Very smooth. My car felt very stable at that speed but I imagine if there had been strong crosswinds it might have been a different story. As relatively light as our cars are for their size, they act like a kite in crosswinds!