Don't know what they gave you for a 100HP tuneup but NOS used to give some bad advise. There tuneups were dead rich and they were slow to tell you to take timing out. What this causes is detonation with fuel puddling. At 100 HP you can get away with a bad tune but why would you want to.

For a 100HP shot I would run a .053 nitrous pill. Depending on fuel pressure for the fuel pill but, a maximum of .047 with 6 psi of fuel pressure. If you have something in the low .04's or maybe even a .038 may be necessary to get a good tune.

Like someone else said 37 degrees of timing is a lot. Most of these engines will run better at 32 degrees. Roll the timing back to 30 if doing it with a retard box. This should be safe. If you get a retard box keep pulling timing until the car slow down. Tune for MPH sense this is the best observation of HP.

Contrary to popular belief. Lean is Mean and fat will hurt the health of your engine. So if it is lazy and your buddies tell you to add timing they are probably full of bull. Try a smaller fuel jet or lower fuel pressure to the nitrous fuel soleniod. Please watch your bottle pressure if you do not have at 850 it aint going to run. You should shoot for 925 PSI or better yet buy a cheap Harbor Freight temp gun and get the bottle to 92 degrees temp. This will provide the necessary pressure.

Happy spraying.

Leon