If it starts and you are satisfied with the performance, then run it as long as possible. Keep maintaining it and watch the oil level. When you mention that the ac makes it run smoother, it tells me that you might have a vaccum leak somewhere. I don't know how a vacuum problem would affect the performance of the engine. However, I recall disconnecting a vacuum line in the central locking circuit while the engine was running and the engine immediately started stumbling.

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2001 Dodge Ram 2500 Cummins Turbo Diesel - 4x4, auto, 3.54 gears, long bed
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'92 300D 2.5 Turbodiesel - sold
'83 300D Turbodiesel - 4 speed manual/2.88 diff - sold
'87 300D Turbodiesel - sold
'82 300D Turbodiesel - sold