[Monte]

The octane point that Ken brought up is another good one. When you go to put premium in your tank, if the person before you got 87, there can still be from 1-3 gallons of 87 in the hose depending on where the mixing valve is. So if the last time you filled up was say 5gallons, 3 of them could of been 87 giving you a total octane of only 89 for that fillup. When tuning higher HP pump gas cars this becomes critical as you can melt a motor due to bad gas at the pump when there is no knock sensor to save it or if the retard doesn't come in quick enough. I always tell people to completely drain and fill their tanks every time so you know that 90% of the fuel will always be 93oct (as long as the right fuel is in the right tank at the station). Also sticking to the same station is a good practice so you know you are always getting the same blend of fuel.

But your biggest issue was your a/f being WAY too rich.