The autozone code only tells you which cylinder is mis-firing.
Since hubby seems to be an experienced nitrous user, it'd be fairly obvious why a certian cylinder would be
a. mis-firing
b. smoking
c. running rough
d. didn't have as much balls as before (Love the choice of words)
a. could be simply a bad coil boot or spark plug {plugs are often closed up/broken by nitrous)
b. smoking generally means you have "nicked a piston" or busted a ring lang which is common when using nitrous
c.busted ring land or otherwise comprimised combustion chamber/cylinder/headgasket
(depends greatly on the color and composition of the smoke)
d. when you lose a significant amount of power, consider that losing 1 of 8 cylinders is a considerable amount of the engines output
If you add ABCD together you wind up with long term detonation (probably in-audible) that over the course of many bottles of 100 shot finally took out one of the ring lands, or simply a clogged fuel filter leaned out the mixture suddenly and the car "popped a headgasket"
{if your lucky it's only a gasket and not any of the "hard parts mentioned above)
WITH that said..
I would pull, inspect and replace the #8 coil boot and spark plug.
If the problem continues.. STOP.. and R&R the motor
R&R= Remove and Replace
they are cheap motors, no sense in "opening one up" other than to see what broke. Too expensive to repair when the junkyards are full of "willing nitrous swallowers"