Chet's back?
I have Jet Hot coated headers. I run water injected above 2500 and below 5700 rpm. Moneysucker and Brendella are right about heat and Jet Hot coating. I can't speak for Rewarder or other coatings...haven't tried them.
Jet Hot survives fine if you inject like above...and don't run dry for long. At CBBB I had a loose wire to the injection controller, thought it was a plugged solenoid. I ran dry upriver to the ramp, taking it easy, maybe 10 minutes or so low speed cruise. That was enough to dull the "near chrome" finish 4-6 inches at elbows with some discoloration at the collector. Also small areas of flaking or coating roughness on the elbows near the exhaust flange...that with a well timed and tuned engine.
Don't get me wrong, they still look good overall and I'd pick coated over chrome any day for a number of reasons. And Jet Hot will re-coat them for free (3yrs). But Jet Hot coating will color locally at hot spots if run dry, just like others have posted.
Not sure why NJBA Donut Hole's a jerk about it.
jer