There are actually two on the back of my pump. One is a stop bolt for the accelerator linkage the other is the rack dampener. The rack dampener is lower, further from the block and between the IP and the oil filter housing kind of behind the oil cooler hose.
There's also a bolt between the IP and the block which controls idle speed.

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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