Did you get the last issue repaired - the stalling when cold/won't stay running until it's warmed up? If so, then what was the issue/repair?
If everything is working properly and the only issue you are having is the pinging, then based on that you mentioned you have no knock sensor installed, I would *** U ME that you need the knock sensor. The primary purpose of the knock sensor is to change the timing to avoid detonation/pinging. But, I'll repeat, if you are having other issues, then I would address them also.
Did you ever find anyone with a datalogger to see what is happenning while your driving?