By any chance has the car lost any power or seem to have its power in a higher rev range??
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Max..1989 244 DL 5 Spd., Bilstein HD, Turbo Swaybars, Poly Bushings all round, Turbo Wheels, Black leather interior, Electric mirrors, LED dash and gauge lights.

Along with Rob's suggestions check your airbox thermostat. Unplug the preheater tube from the bottom of the airbox and see if the pinging is reduced. If so, the thermostat has failed in the hot position - very common occurrence. New ones are quite cheap at FCP Groton.

If all is well on the air intake side of things, timing is correct and you have fresh plugs of proper heat range, it sounds like carbon buildup. Our 83 pinged badly at 150k mi on anything but premium fuel and a little even then. Compression checked at 185-200, which is higher than brand new. For other reasons I had to pull the head a couple of months ago, and in the process, cleaned a fair bit of deposits from the chambers and squish durfaces. Pinging pretty much gone - on 87 octane.
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Bob (son's 81-244GL B21F, dtr's 83-244DL B23F, 'my' 94-944 B230FD; plus grocery-getter Dodge minivan, hobbycar MGB, and numerous old motorcycles)

You could easily retard the ignition another few degrees to help alleviate this. I'd also suspect a lean condition- that often exaggreates pinging.
Look for leaks in vacuum hoses, the large air hose from AMM to intake, injector seals or an intake manifold gasket leak. Mine was hard and crusty in my 86, and I found splits in the intake air hose.
None of these are expensive for a home mechanic ot fix, using parts from FCP Groton or other online suppliers.

This also ought to fix the cold bloodedness of the car. Also consider richening the mixture using the screw on the AMM, but only after fixing leaks.

Good luck with it.
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Rob Bareiss, New London CT ::: '87 244DL/M47- 230K, 88 744GLE- 220K, 82 245T-181K Also responsible for the care and feeding of: 88 745GLE, 231K, 87 244DL, 239K, 94 855GLT 189K