I was at little sahara last weekend and a friend of mine was also on a stock 700xx both of us had glowing exhausts after riding at night, They would calm down to a dull redish glow after a minute or two of idling. He was running 87 octane gas and i had a mix of 91 and 110, and both our exhausts glowed about the same. I think its partly due to the high performance level of this engine and partly just the thin design.
Take your pickup out on a dark night, let it warm up, then get out on a secluded road, and hammer it. Run it up to 100 mph or so, then hit the brakes, stop, kill the lights, pop the hood, and look. Unless they're covered up by heat sheilds or something your exhaust manifolds will very likely be glowing red.