With the centrifugal advance in the distributor it's critical to set the engine timing when the engine rpm is low enough to prevent the advance from engaging.
Lower the idle to ~600-650 rpm and with timing light on cyl #1 look at where the point of engine rpm is when the advance starts to engage. It should be ~900-1100 rpm. Many people forget this effect and set the timing when the advance is partially engaged or when the advance mechanism is dirty & stuck or when the springs are worn out and it engages too early. Before you set it, pull out the breaker plate and clean out the weights and lubricate.
Set the timing at 18 degrees btdc when the engine is ~700 rpm and then raise the idle afterwards.
If the distributor has been replaced with a later aluminum body dist there's a good chance that the springs alow late engagement of the advance, and when you try to accelerate, the timing is not advanced enough, causing pinging. In this case you should replace the springs and get the advance to engage earlier.
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'89 245 Sportwagon, '04 V70 2.5T Sportwagon