I need all you nitrous guys...

Have you actually checked with a timing light that the retard control is pulling the timing out? I had a bad box that was brand new.....MSD had to send me another so you need to check it. Also what fuel pump are you running? You need at least a 140gph pump IMO. Do you have a seperate regulator for the fuel solnoid or is it "T'd" off the carbs? The fuel solenoid needs to be on it's one regualtor. What size fuel lines? Supply and Return? For an Example I run a Mallory Comp 140 pump -8 supply and -8 return to the regulators and -6 to the carb and fuel solenoid and -4 to the n2o plate. You should be running at least -8 supply IMO because you are feeding a carb and nitrous system now and that's all at full throttle when the demand is the highest. I use a Mallory bypass reg for the carb and a Quickfuel dead head style for the fuel solenoid. I use a T'd off the supply line from the fuel pump before the carb regulator for the fuel solenoid supply. As for you bottle heater...good move. Here's a nice little piece I ran across when I was researching my nitrous system:

http://www.dynotunenitrous.com/store/scripts/prodView.asp?idproduct=43

It's a adjustable pressure switch that controls the bottle heater. You can set it to shut the heater off when the bottle pressure hits a set number. I have mine set for 950 psi. It's really slick and works perfect. Also what kind of plugs are you running? Recessed tip plugs should be used to decrease the chances of detonation and decreases the chances of the flame being squashed. The nitrous is raising the cylinder pressure exponetionaly and it will squash the flame depending on the amount you are spraying.