I suggest you give the tech guys at Cummins a call....they are very helpful and should be able to answer your question. Your numbers don't appear unreasonable except for the 1400 reading. Usually anything over 1300 for any length of time should be avoided....our Banks system on our 8.3 ISC will begin to dial back boost at that point after a moment or two. Also, you may want to ensure that the person who installed the pyrometer did not "splice" any of the connecting wires, especially the thermocouple lead. As I recall, that may upset the gauge calibration. Also, air intake leaks and/or dirty air filter can raise the exhaust temps....that is per the Banks folks.
PLEASE let us know what you find out....Thanks!
2003 Fleetwood Revolution DP