I bought the whole kit when I was upgrading my 77300d from loop to pencil. Once I got it, I couldn't figure out why a new relay was necessary so I just tied in the first pencil plug the same way as the old loop plug and have been using the old relay. Kept the new one as a spare. I guess the afterglow does provide some advantage.
I assume the replacement relay will also serve to substitute for OE relays on the later pencil plug engines??

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13