ultimately the nitrous system is limited by the inner diameter of the hoses between the tank and the solenoid, any subsequent fittings between that may have smaller diameter than the hose, or a solenoid that might have a smaller diameter.
Usually the nitrous jet will be the limiting point, but if you get to the 175 horse range, on some kit's its the hose fittings, and or solenoids.
1997 Sport - Work in progress:>
MP BB 304 Teksid 4v- w IC'd / Ported M112
Eaton pulley puller (VMP or BF preferred)