One of the Saito engine traits (all mine at least) is that they will still run at a far leaner setting than many other brands. Other brands start coughing or losing lots of power before the Saito's do when you lean them right out.
If you went from 5% (or whatever) nitro to 30% heli fuel, you have just leaned out your engine sh#tloads. All that extra nitro equates to extra oxygen to burn, if you dont richen it up to counter all this extra oxygen, it will run leaner, and hotter.