When does it start smoking? If it smokes when you first start running, that might be an electrical problem in the engine. Smoke after a couple minutes of operation might be excess lubrication burning off. Neither are good. Try taking the shell off the loco and look for anything obvious (lube dripping off everything, scorch marks on the frame or shell). Then try running it with the shell off and observe where the smoke is coming from. Also, you said it had a D&H paintjob. I don't recall LL offering a D&H paint on the GP38. If someone painted it themselves, you might have excess paint burning inside. Let us know what you find out and we'll go from there. HTH