The more I think about it, I don't think it could be a compression or turbo issue, because it runs fine on vegetable oil. In fact, I can tell when switching over to veggie when all the diesel is out of the IP by the way the engine quiets up and stops smoking and stops the nailing/missing noise which it makes on diesel. So I am almost positive this is a fuel issue, but if it's not the injectors or the timing, I don't know what else it could be. I can't imagine the IP is going out if it runs good on veggie, I would think that because it is thicker that vegetable oil would make any IP weakness even worse. Although the vegetable oil is being pumped into the IP at a much greater pressure than the diesel, but still that doesn't seem like it would affect anything. So I guess the key to my problem is figuring out what mechanical issue would be more evident when running the vehicle on diesel fuel.

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87 300D - Running on Veggie oil; 260,000 plus miles; Original #14 head