I did not purchase the HPOP Gauge Pigtail Harness, can I still install this gauge on my 7.3L/6.0L Ford Powerstroke?

The HPOP Pigtail harness is not required to purchase to install an HPOP gauge to your 1999-2007 Powerstroke. The HPOP Pigtail harness eliminates you from having to tap into the vehicle's factory wiring harness. If the Pigtail harness is not purchased you can tap into the factory HPOP harness signal wire for your installation.