Have super-short injectors and the fuel rail doesn't reach down far enough? (e.g. Siemens 630cc "Shorty" in AEB/AGU or 16v). The Genesis "Unspacer"; is your solution. These slip on top of short injectors and seal against the o-ring. Powder coated in gloss black, the Unspacer has an o-ring on top that seals inside the fuel rail. Installation takes mere seconds. They're inexpensive and include rail clips, too! Parts priced each.
(Pictured in blue for display contrast.)