greg,
I have had my injection pump adjusted so the engine is getting more fuel. Before the adjustment, the tractor ran smooth but had absolutely no power. Of course, with more fuel, more smoke. Under load, it will exhaust a slight/moderate amount of greyish/black smoke. Several "diesel people" I have talked to said that the EPA emissions regs. are not allowing these engines to run the way they really could be.
One other thing I have done is the change the exhaust routing. Although the direction of the exhaust did not change performance, the fact that when modifiying the the exhaust pipe, we found that the original pipe was bent so sharp that it was nearly kinked. I don't know how it even ran with the exhaust nearly plugged.
jwstewar,
I think you should have the relief valve settings checked. I can easily stall the engine from full-throttle while in low-range. The engine will stall out before the tractor ever thinks of breaking traction.
Joe