I think you had the right wire, but you unplugged it from the starting circuit cut-off relay, which is the source of the voltage. With the connector plugged in you should have 12v at the Red/Blue wire. If you don't, then look at the Red/Black wire (triggers the relay) and the solid Red wire (source of fuel pump voltage). Both should have 12v.
Red/Black comes from the cutoff switch and the solid red comes from the 'fuel injection' fuse.
If Red/Black is 0v, then check the cutoff switch. If solid red is 0v, then check the fuse. Your original complaint of power reducing makes the fuse unlikely.
There have been LOTS of issues with the cutoff switch degrading, causing a loss of performance. I am leaning that way.
Did you check your private messages lately?