I have been running the juice verry successfully for years now. The main thing is that you need to retard the timing 2 degrees for every 100 HP of juice. The second is that you must have fuel delivery. Remember it is not the nitrous that makes power it is the added fuel. The oxygen in the n20 will allow that fuel to burn. One more thing is to never dead head the regulator that goes to the gas solinoid. This is very important as the reading on the guage will not be correct. I use a #3 an fitting for a return line off of the inlet to the gas solinoid. Cut off the end of the flare, drill out the fitting so you can install a #32 size jet from some old fogger unit. This will allow just enough fuel to bypass the regulator so you canset it to the desired pressure setting. This is cheap and it works.
I have a 9 to 1 forged piston 440 in a dart. Small cam, street driven and it runs only a 12:02 off of the juice and a 10:50 on the juice. I have put over 100 pounds of juice through this motor and it runs like new. Total timing is set at 32 degrees, fuel pressure is set a 6.5lbs.