so there are just 2 coolant ports
, one on either side of the stove pipe ??
Use 1/4" pipe tap and brass plugs ??
then you said remove something from the UIM gasket ?? I dont get where the nickle comes into play ??
Yes, 2 ports.
Yes, 1/4" NPT tap, you will need to enlarge the hole a little.
Brass plugs are fine
Yes, this is used on a leaking UIM, this is the fix
Remove the O rings from the gasket, (coolant passages) a nickel fits perfectly. Seal it all up with red RTV