In my experience pinging is much louder than valvetrain noise. I recently replaced my intake gaskets, following factory service manual directions exactly, using quality gaskets. I even put in new injectors at the same time.
First time I tried regular gas after the above work, pinged like hell on a warmer day going uphill. Put in premium ethanol-free and it hasn't made a peep since. Even today and yesterday, it's been super hot here lately and I was driving up steep gravel roads today without issue.
In my case, it's not intake gaskets, it's not lack of fuel from dirty injectors, fuel pressure is good, fuel filter and regulator is new, no vacuum leaks. Cylinder compression isn't as ideal as it could be (good numbers, just not as even as it should be but far from a dead cylinder). About the only thing I can think of is that the engine is worn and with blowby, enough oil is getting into the combustion chamber and carboning up. I seafoamed when I first got the Ex but always ran premium in it. Now, over a year and a half later, I'm sure that carbon is built back up (if the Seafoam even did anything).
If it is an oil issue, perhaps a catch can on the PCV valve and then Seafoaming the hell out of the engine might prevent it from coming back, or at least slow it down significantly.
