[240 2NR]

Well if you plan to run the lowest octane available, then leave it alone as the book calls for 91, so running 87 or 89 is with the "safety net" nissan left in the timing so just such a thing could occur without detonating the engine to death. If you plan to religiously run premium then a couple degrees shouldn't hurt anything and really will help burn that more efficiently. Safely you should be able to go to 24 degrees BTDC (22 is spec). Any more than that and you may wish to start dyno tuning to see where the power really peaks or falls off so you can accurately guage where the timing does the most good (then when you know you can tell me). Mine is at 23-24, advanced from 21-22 and it's hard to say if it really did much, if nothingelse I think it improved my idle). Remeber to listen for pings.