The Higher the octane the harder it is for the fuel to be ignited through compression and will be ignited by the sparkplug. Pinging or Knocking is cause by preignition of the fuel because of compression. If your going to advance the timing you must raise up the octaneto atleast 89 or 91.....i had my old LS and i got the car from someone else the motor was a beast in the higher RPM band...it would kind of sound like VTEC but always open..i was curious to see what was going on and i seen he had the timing on the intake side advanced one notch on the belt and sprocket....i never looked to check the exact timing but i figured it was above 24 degrees...it was great for an al motor setup i had going the car was a little rough at idle in cold weather but once she was warm it was all good....i wouldnt have any great power till 3K which was great for launching....try it if you like....