they run rich because honda has an awesome fuel delivery system.. The problem is in the piston material, for quieter long lasting motors they use a very high silicone content piston material. It's perfect if you're just driving around but when you add nitrous the cylinder temps are very high and the silicone material in the piston let's go. That why when you see a turbo honda that had awesome tuning on an OE motor and it finally let's go, you'll find collapsed ring lands.. I've seen some break at the skirt..