You can safely run those pistons on 93 octane. And yes you may end up advancing the timing.

One thing a lot of people forget, is that JDM p30 pistons yield about 11.5:1 compression on an LS/VTEC and have a flat top. The flat top of the piston allows the flame to travel a greater distance at a faster speed. The result is a more complete burn of all the fuel in the cylinder equallying more power.

Don't let the big dome of CTR/ITR pistons mislead you. Sometimes smaller is better. In this case, on a street engine, p30's would be perfect.

Jay