just wondering does the light come on at 90 mph or just when you hit it to WOT, and how dose the engine run with the light on,
Im not sure about the tuner you have,(never used one) but for a test you might want to turn it off if you can and test it, to see if you have the same problem,
When you hit hard on it you do stress the engine components, you might have something that might be going out on you..kind of a advance warning,
(Just my 2 cents here) You might want to stay away from the hitting WOT Untill you get it scanned, maybe baby it a little, I would hate to hear you broke down on the road..
I believe if you can ,maybe call around the area you might find an autostore that does codes for free, im not sure were your at, but around here in Michigan we have chain stores called Autozone and they do free tests..also if you know someone with a Superships programmer you can also use those..
Or at least maybe see is you can find some place in route back home to run codes at,..