I started with NOS in 1993 using a Wizard of NOS kit from Trevor Langfield. I continued with this kit with various modifications, (drilling the holes bigger), up until 1998 recording a best of 7.51 @ 174mph on a 1.90mm single NOS jet, (Trev systems used a single jet in the solenoid). Fuel pressure was 4.5 psi, ignition timing on the 1428cc engine was 29 deg sucking C16 through 39mm Amal carbs. The rest of the engine was nothing special. A home ported head with 37/31 valves at about 11.5:1 CR with 480/460 cams.
1999 was the year of molten aluminum and ashtray production, (holed pistons) trying to get even more out of the NOS system. In the end I changed to individually jetted port injectors but retained the Trevor solenoids without their jets.
2000 saw changes to fuel pumps, nitrous lines etc right through to 2003 with the addition of a Holly pump and some monster solenoids resulting in the 7.1's and 190+ mph's. However these came at the price of torching the heads.
The heads broke because they are not strong enough when you match them to a 1500 block and pistons with monster valves and an 8 plug conversion. You just run out of aluminum to hold it all together.
However to help answer the same question, "how much nos can I use", I have attached the run sheets recorded for 2010 the year we broke into the SIXES. The ONLY Kawasaki in Europe to do so and second only to Chris Hall to do it with just NOS. Feel free to use them, I want to race someone.
What happens when the parts get frightened of the dark. Click
I would recommend using Chris Hall's Striptune program to get the best from the chassis as you increase the power
Also of use is this list "Drills.XLS" . This helps me and others in working out the percentage increase in flow you will get when you go up on jet sizes.