The computer has a rev limiter built in...so you can't over rev the motor. That "roar" you hear, is, in all probablility the fan turning on to cool things off. Nothing to worry about.
My older 2001 does not have the "tow" feature you have, but does have "overdrive on/off" which, I imagine does the same thing....but you have to do it. (push a button). "Overdrive" will kick out on long steep hills (now y'gotta step on the gas) and the dash a/c cuts out (too small a vacuum cannister)until you start the downward side of the hill or until the motor slows down, letting vacuum build up. Definately an annoyance on a hot day.
My experience with the V-10 (over 55,000 on the odometer right now) is that it is bullet-proof. Just keep changing the oil and filter on any schedule you make (3000 for fossil 7000 for syn) and it will probably go on "forever".