The manufacturing tolerances issue in M+D jets was what was related to surging after the start in South African conditions and before they reached the certification stage IIRC. My early pre- certification jet didn't have that problem. Over 135 starts during my time of ownership (mostly ground and air tests in both Scotland and South Africa) what I did find was that it didn't start reliably in cold UK conditions with diesel fuel but was fine with jet A1, whereas in SA it was very unreliable on jet A1. At the suggestion of the factory I started using premium synthetic/petrochemical diesel fuel (Shell V-Power Nitro) and with that it started 100% in both cold UK and hot/high SA. That stuff contains no biofuel btw.

The other thing I learned myself was to use an additive such as Biobor to prevent microbial overgrowth from clogging the fuel filters. 1 ml added to 10 litres was all that was required.