It seems you've already addressed the ignition system, so I'd maybe be looking elsewhere. Warm the motor and run the valve lash again. Back off each rocker until it clacks, then tighten down slowly until it quiets, then give it another half turn. You may be holding one or more valves slightly off the seat. It might also be one or more burnt exhaust valves. Do you have time to do a compression check on all cylinders? If you do, be sure to wire the carb primary blades open so the motor can breathe.

By the way, you installed the regulator so that just the carb is regulated right? You don't want the nos fuel solenoid regulated down so far that the motor goes lean when you spray it.

I have to leave to go to work now, so I'm in hopes that Denny, Mike or one of the other diagnostic gurus can help you further. It's tough to diagnose a miss by long distance.