Fatter wiring

Thanks for the input guys, after doing some reading I see this is not a new thing.

After a drive I on a hot day, I felt the wiring behind the amp gauge and was shocked how hot it was.

I would like to keep the old amp guage and run new wires inbetween Alternator and battery, bypassing firewall connector, mostly for reliablity. Also I am an electrical nut job, that likes to tinker. I would like to look into the Diode fix, but I am not smart enough to find it, so if you could direct me.....

Thanks so much for your input on what appears to be a very common question.