Looking at the whole story, I would not recommend upgrading until you diagnose and fix what is physically causing the engine issues. Sometimes it 's merely the newness at fault and a longer run in period is needed to loosen things up. Otherwise, whatever the cause, an electronics upgrade will help maintain speed but be constantly straining to do so.
An ERR cruise commander can sure produce a jewel out a smooth performing tmcc loco. Gotta have a healthy patient to begin with, though.
Bruce
