High compression blues.

j par said
Isn't that why you retard the timing for nitrous?

Well sure, but from the sound of it, his timing would need retarding to the point that it would remove what power the nitrous added.

He's on the ragged edge now. He'll probably still detonate in the summer during heat soak.

Nitrous engines "should" be specifically built for nitrous. Wider LAS and generally lower compression than what he has.