30mph was the limit. Could get no more except on a few flatter sections where I was able to get about 3400rpm's for a few hundred yards.
I'm disappointed that the boost line was disconnected because now I don't know how it would perform that heavily loaded and I don't feel like loading it up again and giving it a try.
I was misled by the fact that I was heavily loaded. I attributed the slow performance to the load, whereas if I'd have been unloaded I'd have checked for problems.

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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