I'm not saying it has to be dry. To me that depends on the duty cycle of the injectors before you add the nitrous and how much room you have to play with. If you have plenty of fuel left in the injectors to match what you want to put in, then by all means run a dry setup. If you are running a good direct port system you eliminate the dangers of fuel puddling so I don't see that as a problem. The wet system would work fine that way, then you only have to worry about the capacity of your fuel lines. The main benefit is precise metering of nitrous for each cylinder which adds up to More and Safer power.
warmonger
Former owner of '99 CSVT - Silver #222/2760
356/334 wHP/TQ at 10psi on pump gas!
See My Mods
'05 Volvo S40 Turbo 5 AWD with 6spd, Passion Red
'06 Mazda5 Touring, 5spd,MTX, Black