I cured nailing in my 87 SDL by replacing delivery valve seals that weren't leaking externally. Others have gotten lucky with just a fresh set of heat shields or injector seals.

Gus Pfister is among the most knowledgable in the country when it comes to these fuel systems - http://www.bayarea02.com/features/pfister-interview/index.html I heard he still doesn't take credit cards.

Sixto
87 300D