I had an agonizing two hour ride tonight trying the hear the World Series on AM radio. For years there's been the static interference that sounds like the antenna is connected directly to the distributor cap. After googling and searching and not finding much, for fun I cleanned the contacts on the back of the head unit. There was no visible dirt showing up, but miraculously the horrible whirring static is completely gone (with the game long since ended). One of the plugs must have been partially pulled from pulling on the radio. I can't say this could work for everyone, or that it won't come back on my return trip, but wow, I'd been suffering all this time.
Have fun
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'97 855na, Mobil 1, K&N, various IPD's and eBay's

I have the same issue for last two years and found no solution. Sounds like it's worth a try. When you say contacts, which ones do you mean. At back of the radio unit or at antenna in trunk? Thanks

Radio unit is all I did. unplugged the connections, cleaned with alcohol swabs and plugged back in. I hope it works for you.
Thanks,
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'97 855na, Mobil 1, K&N, various IPD's and eBay's