Since the HP boost is so low on a sneeky pete system, would i still need to retard the timing?

 

I would just to be on the safe side. 1 or 2 degrees from base timing can't hurt.

 

You generally don't need to retard any timing until surpassing 125-150 HP shots. That is assuming that the timing is right (not overly advanced) in the first place, with no detonation present without nitrous. The cooling effect of nitrous will decrease the chance of detonation wth smaller shots, unless you're too lean and then that is an air/fuel issue, not a timing issue. At levels higher than 125-150 HP shots the nitrous/fuel mix is so dense that it burns much more rapidly and thus you need less timing advance (retard) before TDC. The 10-20 HP shot from a Sneaky Pete just isn't that dense to need retard.