Did you get the exhaust REALLY wet? Were you charging the mud coming in hot? Sounds like a cat. problem to me.... Have a buddy rev it to 2-3 grand while your head is out pack listening to the exhuast. If it sounds whsitley, then somthing is obstructing it. You can also temporarily remove the O2 sensor and zip tie it out of the way to see if the extra 1" hole will help power. Does it run fine cold?