I believe partial throttle valve noise may not be correct. I would think fuel knock and would check the distributor and determine what the timing curve looks like. Good luck..
Sadly...the distributor on a 2nd gen has nothing in it to affect timing as far as an ignition advance curve.
It has the cam sensor in it....and you don't want to move the distributor because it will mess up your fuel sync. Unless you have the proper tool to check that, and it's not a Wal Mart scanner!
Suggestions more in line might be a check of the plenum to see if has pooled oil in it. This suggests a blown plenum gasket, which will cause pinging. Other symptoms are slight oil loss and poor mileage.
Could be sludge buildup in oil passages causing the lifters to not pump up, but in such cases it'd be prevelant throughout the run cycle
Perhaps dribbling some seafoam through the throttle boy to clean the valves and running some Chevron techron fuel system cleaner through the tank might help.