To relieve the fuel pressure, wrap a clean towel or rag around either the cold start injector fitting or the union bolt (banjo bolt) at the fuel delivery rail. Slowly loosen the bolt holding the fuel line and allow pressurized fuel to escape into the rag. Do NOT allow fuel to spray from the fitting; always wrap it in a rag.
Pressure may also be relieved at the fuel filter if desired. Tighten the union bolt.