Well you might not want to hear this, but a fully functioning EGR system, can actually make pinging worse in an older high-mileage engine. Now the ruptured diaphragm may have contributed to a lean A/F. The EGR system is supposed to dump a small amount VERY hot exhaust gasses back into the intake, from where it goes back into the cylinder, to take up space.(Actually it's supposed to reduce NOx, to reduce pollution. Pollution which actually comes from the reduced compression ratio, which was introduced because....yadyadayada.) Anyways the hot gasses can wreak havoc on those hi-mileage engines. Many times this can be traced to excessive carbon deposits in the chambers. So you probably need to try and flush those out. You can purchase products to do this. Some go into the oil, some the gas, and my favorite is the stuff you pour down the carb throats. It is by far the fastest acting. After your chambers are cleaned up, your problem may disappear, and the fully functioning EGR will be a non-issue.
Be advised tho that even with a fully functioning EGR valve, the system may still not be fully functioning.This is because the passages inside the intake may be fully or partially plugged with carbon. There is an easy test for this.With the engine idling,and a functioning valve, just apply vacuum to the diaphragm. If the passages are open, the engine will usually stall. If the idle changes not a bit, then the intake needs to come off, and the passages cleaned out.This involves a lot of chiseling, and then a trip to the engine shop for a caustic bath.You absolutely don't want those carbon pieces getting into the chambers.While most of them might harmlessly pass through, it is possible for some to lodge in places they can do damage.
One of the biggest causes to pinging (after too much timing),is chamber temperature.Chamber temp is principally controlled by correct A/F and timing, but the cooling system also plays an important roll, as does the inlet air temperature.So you need to verify those systems are working as well. If the carb is sucking hot air up through the carb heating system,fulltime, this will not be good. So in addition to checking the cooling system temp, it is very important to verify that the carb is getting fresh cold air.
If your engine is covered in dirt and oil,give it a pressurewash.
Verify the exhaust system is properly functioning. If it is restrictive, it will heat up the chambers real quick.
Make sure the car rolls easy, as in the brakes are not dragging and the tire pressures are up.
That's all I can think of for now....