What was your ignition advance? I have run this car lean before with the water on, but didn't leave it that way out of fear of blowing over time.

Because of the ECU I was running it was not as shown on the data screen. In actual fact is was about -3deg or 3ATDC in that range. This is due to the leading and trailing spark plug firing together.

On other cars with more conventional L&T splits I run about 10 to 12 degree advance at that power level to give you an idea.