2 degree TA

Here is my opinion based on my experience with both building engines and on my own personal Nismo...

A small timing advance on a completely stock motor will not do very much if anything at all. In colder weather it will help a small amount on even a stock motor because there is a slightly more dense charge that can be combusted more readily.

However, if you do any breathing mods, like a new exhaust or a Cold Air Intake (CAI) it can make quite a bit of difference. The freer your motor breathes the more advance you may need for it to run smoothly. In other words if I get more charge into the combustion chamber and make it easier for that charge to leave the chamber during the exhaust cycle then the charge may need a slightly sooner "burn" to use the charge more effectively. And it should help a slight amount with idle, power, and mileage.

The one caveat here is that if you manage to advance the timing too much you can cause detonation. NOT GOOD! Even with the ignition knock sensors to retard the timing it is still hard on the motor and damaging to any performance gains.

One last consideration, the effects of timing advance and breathing mods is DEFINITELY dependent on temperature and weather conditions as well. When it is cooler out your motor can deal with more aggressive timing, during hot summer months, especially in the SouthWest like AZ, NM, TX, or Southern CA desert areas those 110+ temps can be damaging with aggressive timing setups.

Just my 2 cents.

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I've noticed GREAT improvements in performance by doing all of the following:

CAI
Custom Exhaust
Change out Fluids to 100% synthetics
Remove WOT restriction
SuperChips 87 Performance tune
2 degrees timing advance

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I noticed more performance gains from the WOT removal than the SuperChips tuning. However the timing advance and a slight RPM increase (+25 RPM) did improve my idle quite a bit and I do notice a power increase across the whole power band but all the other changes made a LOT more difference.