Didn't put the car on Dyno so no numerical HP increase confirmation. However, the car is pulling significantly harder in straight line that's for sure. I've also replaced a new set of oiled-air-filters (old ones are too dirty) which help the air-boxes to maximize its performance as well.
This is not doubt one of the best mods for a 360, in look & performance IMHO. You can see the rest of the modifications on my 360 here: http://www.jimmy540i.com/ferrari2.htm (click on the pix to see details). Cheers!