they can handle a little bit of nitrous just fine, but stay away from the nitrous kits available for these engines. they don't inject extra fuel to compensate for the extra oxygen, so they just run lean and more often than not just melt the piston without making any extra power.
I've been toying around with a system that squirts both nitrous oxide and propane into the inlet stream, but haven't put anything to market yet. if you want to fab one up yourself you'll need a nitrous bottle and a propane bottle (I'm using the NX 1 pound bottle and coleman 16.4 oz cylinders), gas pressure regulators for each one, and then the usual system of tubing and jets and solenoid valves. go 1:1 on nitrous/propane mix and play with the jets until a plug chop reads right.