I just realized the sequence should be Bank 2 lower (radiator side) to determine if main cat is plugged, Bank 2 upper (radiator) to determine if Bank 2 precat is plugged, Bank 1 upper (hardest one, close to firewall) to determine if bank 1 precat is plugged. You don't need to mess with bank 1 lower as bank 2 lower will take care of that issue too (if it is an issue). Good luck.
