Andy:

I would try to get some information out of the dealer. Barring that, I guess I would start with a 750 ohm resistor, which should be about 6 degrees of retard. I start here, because that value (750 ohms) had the same retard value for my car and for JimFs. Should be the same for yours, but no guarantee.

If no pinging, and you are happy with the performance, that's it. If it pings, go to a 470 ohm resistor. Keep reducing resistance until pinging goes away.

Remember that under load on a hot day is the worst environment for pinging to happen. If it only pings in those conditions, and never under normal driving, you shouldn't have to make much of a change in the direction of retard to cure it.

Of course, you should really check the timing with a light and verify that it is within specifications.

Good luck

Tom