0411 dies at full throttle.

First of all thanks for all the help on getting my initial tune on the Jet boat figured out, AFR is good, engine runs fanastic!

A new problem developed this weekend and i'm kind of stumped. I can ride around at any rpm and any amount of throttle, but if I hold it at WOT for more than 5-10 seconds, the PCM completely dies. I lose communication with it through HP tuners, I've double checked wiring connections, grounds, battery connections, etc... It first happened friday, and I had to let it sit for 3-4 minutes and It would fire up for about 15 seconds and die again, this wsa repeated for roughly half an hour attempting to make it back to the boat ramp. after reaching the boat ramp, the PCM would not respond, and engine wouldn't fire for over an hour. Saturday morning it fired right up and ran fine, I replaced all relays and checked all connections. Went out saturday afternoon and rode for around 30 minutes, finally punched it to full throttle, and it died, immediately refired it and went about a 1/4 mile or so at 80% throttle, went to WOT and it died yet again. So i loaded it up before it stranded me again on the water. Has anyone else experienced this with an 0411 PCM?

It's not VATS.

Just like 2xLS1 said, it's not VATS.

I've only seen this a few times. Here are a few things to check.
I tuned a Toyota PreRunner truck last year that did the same thing. It would cough/spit/misfire, then go dead anytime you went above 3/4 throttle.
It was the spark plugs. They were installed by the engine builder, and gapped properly, but they were the wrong type plug. Turns out they were a non-resistor plug.
We installed some NGK TR7 plugs in it, and the problem went away.

Also check the plug gaps. The required gap will depend on the amount of boost that you're running.

could be a plug wire shorting out on the headers.... But first, I'd check your Crankshaft Pos sensor. Make sure its seated correctly and make sure the rubber grommet/seal is in there and in place. I had chased a similar problem like this for a long time on a customer vehicle. Turned out to be missing the weatherpack seal on the CPS causing the engine to shut off at WOT.

You can also try logging the CPS revolutions to see if it looks like its loosing a connection or if the pcm is seeing poor readings. Also check for lateral play in the crank shaft with the belts removed. I've also seen built 4l80e and TH400 transmissions wipe out thrust bearings in the motors, which causes excessive runout. Too much will move the reluctor wheel enough to be out of range.

After re-reading your post, my guess is if you tow a boat with this vehicle, you should check to see if you have any exposed wires getting wet. This would surely not make a PCM happy.

What is your alternator charge looking like at WOT?

what voltage is the alternator outputting?