Nitrous is not for the lazy...

I would retard the timing regardless of what the instructions say and sneak back up on the total number that it runs best. Just do it manually to start with if you don't have a retard module, etc. Detonation is a KILLER with n2o tune ups. What's it gonna hurt if you back out 4 degrees and see how it runs for MPH? Then add 2 back and see MPH again. If it slows down, as long as everything is constant, you know you went a bit too far. Get back to your original total number no biggie, BUT, you didn't risk smoking something because it had too much to start with.

Jetting on your carb will not change. You adjust the nitrous/fuel pills to keep things happy and in tune. You can also tweak it raising or lowering fuel pressure in a pinch. Fat tune up is bad too... don't believe the fat is good/safe crowd.

Most of us have some decent money in our engines. Whether it's 1,000 or 20,000, cooking it because you went too far from the start seems risky to me. Call me conservative, I'll err on the safe side and sneak up, than balls out and dead!

Good luck with it.