you will distroy the engine if you continue to let this noise happen.
the timing must be retarded to get the ping out if its that bad.
most of the time if its just a little bit though filling the tank with super unleaded will take out the noise.
the distributer must be loosend and turned in the correct way to ****** the timing and the idle must be put back up to compensate.
the distributer is the ignition timing.
the other thing that could have happend is the timing may have jumped time on the timing belt itself.this is a complely different timing.
this timing is valve timing.
the distributer is ignition timing.
when the distributer is turned you are changing the ignition timing .
you say in your text and i quote .
The service tech only adjusted the distributor fas far as he could to lower the idle.
a tech should never be turning the distributer to lower the idle nor should this be explained in any way to the customer.
if a tech says he dosent understand something stop them rightaway and get your car out of there or get someone else to talk to .
10 times out of 10 if the tech dosnet get it the car wont get it either.
have a competent service tech test and conferm the timing belt or chain timing .
keep me posted