one more thing. You said that there is no vibration. sometimes a vibration can be mistaken as a noise. I see this all the time at the shop.

I only bring this up because you mentioned motor mounts. The mounts in that car are oil filled, and when they go, usually the complaint is "rough idle" which is a misinterpetation of the motor sitting on the crossmember and vibrating. But if the mounts are only sagging and not completely collapsed, it can cause a change in the drive line (drive shaft to diff, trans) angles. and that can cause a vibration. Just thought I'd mention it.

good luck

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Scott