2004 Tacoma 3.4 L 4x4 w/ 79,000 miles.

Truck pings/knocks under any load, through all gears intermittently. It will only do this when at operating temperature and is worse with the A/C on.
Higher octane gas helps a little bit, but not much.
List of things done to the truck recently:

New:
O2 sensors
MAF sensor
Air Filter
Plugs/Wires (plugs about 4-5K miles ago)
Coolant Change
Have run bottles of fuel injector cleaner every once and awhile.

Checked:
Codes/Freeze Frames w/ OBDII Inova Scanner. Nothing shown.
Gas mileage has been very steady, with a slight drop in city driving mileage.
No felt power loss.

Have not checked:
Vacuum lines for leaks
Extra air intake causing a lean condition

I am at a loss gentlemen and/or ladies. Short of taking it in to a mechanic to go through, I don't know what else to look for or check. I really don't think it should be pinging like this. My 94 22re doesn't ping like this unless I'm dropping the throttle in a high gear with the A/C on.

Any ideas would be appreciated.

 

How did the vacuum hose investigation turn out?

 

No leaks detected. Really at a loss here. Seems like the pinging is random at times.
Its prob carbon buildup although seafoam and bg44k stuff hasnt worked.