Oh also, the DPF delete pipe vendor wrote back and stated that I just need to plug the exhaust cooler inlet along with bypassing the coolant lines.

For the exhaust cooler plug it should be something simple, disk shaped, has similar thickness to the exhaust cooler flange, and metal. My search for a 40mm coin is an obsolete $100 Mexican peso, but I don't have one lying around. I will check to see if I have any suitable $1 casino tokens.