Sounds like you have some "pinging" going on. That's a sign of to much timing, not enough fuel,or not enough octane. You can pull some of the timing out. If I remember right you can add and pull timing at 2 degree increments. Also, be sure that you have 93 octane in the car. How far empty was the tank before you topped it off with 93 octane? You can also add a octane booster to the tank. You can also add fuel to the fuel table. Pearl02.