what gauge of wires?

Not too overly sure but arbitrarily going up one size in wire may not be a great idea. Just use what the service manual says.
in my take, If you go up one size in wire on a select circuit the wire itself can now handle more load but maybe the destination item (gauge, voltage regulator, or whatever) may not be able to handle the extra load. The gauge of wire may also be part of the design in that it is designed to fry instead of what is at the other end of it. ??