03's don't have STC or dummy plugs. It's a different HPO system than the 04 and 05-07 models, which use them. The 03 and 04 motors use the same HPOP, but different oil rails and can also develop leaks at the branch tube here: Page 40: Fuel Management System. There is an o-ring kit for it: HPOP seal kit 03/04 3C3Z-9G804-AA