Thank you for the note! It appears I had fixed the errors, but had neglected to upload the fixed version. So, before I upload it to the DLS, would you like to take a look and see if this works for you?
http://carsoncarshops.com/files/YVRR_Ba ... ertank.cdp
As for altering an engine's behavior in surveyor, are you referring to the engine overshooting the spout, or stopping at the wrong place? I'm not sure of any methods to actually alter the engine, but you could salter the AI behavior:
You could add a slow speed limit near the tank, so the train isn't going as fast when it gets to the tank. That might help an overshoot problem. If it's just always stopping at the wrong place, you could try adding a track mark at the spot you want the engine to stop at, then use a 'driver to' command to drive to your track mark, then issue a load command.
Those are just ideas I've seen other people give; I'm not very familiar with the AI operation myself.