Fuel problem?

Hay guys I have been having a weard problem with my car. It seems to be making ping sounds when I give it gas. It dosen't do it when I am light on the throttle; I can get it over 90mph slowly with no problems. But as soon as I hit it harder it makes a sound like marbles banging together. I think my problem is the CA piss gas. I filled up at Sams Club sunday and did not notice the problem utill today when I got on the throttle hard. I just want to get an idea of what else can cause something like this to happen just in case it's not the gas. Thanks

Low octane gas or you might have an EGR problem. The timing in your tune could be too aggressive.

Ok thanks shoebox. I am going to burn this gas out and fill up with some 76 race gas. That should fix it I hope. At least I know what to look at next if it does not take care of it. Thanks