On the 2014 and newer FLHTK, FLTRU, and FLHTCUTG models we like to place the air pressure gauge in panel on the LH lower wind deflector rather than drilling a hole in the dash panel. That way if the system is removed, the panel on the lower can easily be replaced and the bike is back to stock rather than replacing and entire dash panel. There are no issues with a gauge and the radiator or cooling fans on the twin cooled models either. 

Please see the pictures below for examples: