sounds like your using the push to connect fittings at the regulator, they can leak at the reduced pressure. I would install the compression fittings that came with the regulator kit. If the hose is leaking it can freeze the nitrous line and lessen the amount of nitrous coming through.
Did you add and subtract fuel when spraying the 180 psi @ the 180psi number to get best performance, then turn it up to 340psi and adjust the fuel delivery at 340psi?
How many turns out are you running the regulator? I would recommend setting it at 3 turns out (after tuning is complete), this is about the 45 hp most guys are looking for.
