Why does my engine ping with light throttle pressure?

I have the 5.0L engine with about 200,000 miles. The ping I'm experiencing is under light throttle. Under medium to heavy acceleration the pinging becomes lighter or goes away. For instance, at highway speeds with the cruise set a slight grade will make the engine ping. There are no DTC's stored in the VCM at this time. I have thoroughly checked the EGR system and found no issues. I recently Sea Foamed the engine directly and had all most no smoke produced in the process leaving me to think that carbon build up is at a minimum or less.
Thanks in advance
subzero10