For ECU development I put a n2o kit on my RSX. The jet sizes they supply in some of the kits are rather optimistic. I made 25 hp on the "40 hp" jet (0.022). 25 hp is hard to fell - about the same as the AC switching off. The "70 hp" (0.032) jet made about 45 hp, and was ok. I put in a 0.047 jet, which made 80-85 hp.
This was all dry using Hondata to add fuel and pull timing, otherwise I'd be a bit more convervative. The 0.047 jet was too much for the stock injectors - they reached 100% duty at about 7000 rpm. With bigger injectors the power peaked early (7000 rpm) and fell off - probably the stock exhaust chocking it. On the street the car was fairly fast - wheelspin in 3rd gear, big black lines etc. Used 2 bottles, then went on to test something else, have not run n20 since.
Be really careful with n2o. Make sure the fuel system is up to it, keep an eye on the a/f ratio, injector duty etc. Either pull out timing or only run a 40 shot. The good think about n2o is that you can always see the funny side when something goes wrong.