Can you backfire out of the itbs?
 

been doing some tuning and we seem to be getting a loud noise under WOT at higher rpms. Not sure if its the exhaust blowing through something or if the engine is back firing through the ITBs. Trying to determine the possibility of that.

Never experienced that at WOT.

You would have to have your trailing spark really -really- advanced, I would think. So advanced that the trailing was firing about 90 degrees BTDC or such.

Easy check, disconnect the trailing spark and run it and see what happens. I don't think it's possible to have the leading plug open to the intake valve, so without trailing, it should be impossible.