fast pinging

Here is a question for all you guys. I have the timing set at 12*. As I roll on the throttle to wide open the motor pull hard and no pinging. (i use highest octain I can get). BUT.....If I'm going about 30MPH and holding the gas At 3000 and slam the gas down I get a really fast pinging that quickly stops when accelerating Its like the computer cant react fast enough to retard the timing. Any ideas? Ive even backed the timing down to 10* and it still does it the same. Lets see if anybody hase any answers.

thanks in advance.

thanks for the reply...I dosent matter what gear....it does it not matter 1st, 2nd, high rpm low rpm....does it the same. I'm baffled