I've been told you shouldn't abuse an engine past a certain mileage point all my life, BUT, I think it has more to do with condition and maintenance of said engine. I put a 150shot on a 170,XXX miles Mustang GT and ran mid 12s on street tires because I took great care of it. My neigbor blew up a 2003 Cobra with only 40K on it because he didn't take good care of it.
Moral of the story: If everything is in fine working condition, and you have made neccessary supporting mods to the car, do and get a great tune. If you know the history of the engine, and have addressed any issues it may have, and have maintained it properly, I don't see a problem. 111K isn't high mileage these days.
2005 Black ACR
Mopar Stage 3, Mopar Downpipe, Mopar Catback, Booger Shift linkage bushings, Kenwood, Polk, Kicker and Image Dynamics
1990 Mustang Coupe 5.0 - Explorer Powered.