I would pull the injectors and have them pop tested and balanced. The local injector shop around here tests them for free and charges around $70 for adjusting them. They are likely gummed up from all of that un-headed WVO.

Glad to hear that the marvel mystery oil may free rings that have been stick from un-heated veg oil. There are going to be lots of these cars left for dead after bad alternative fuel experimentation soon.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine