i think it has something to do with the lower compression ratio on newer diesels. and the regeneration cycle system as well.

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93 b2200 EFI turbo, reg cab/short box, F2t swap build thread here
92 B2600i Cab plus getting a 82 3.0L 5cyl 617 mercedes Turbo Diesel build thread here
96 GMC 1500 z71 4x4 6.5L turbo diesel
Diesel all the way!!!