whistle noise in radio stepping on accelerator

Have 1990, lately when I accelerate I hear a whine or whistle on the radio, if I go faster whine louder, any ideas??

That's interference from the ignition. Cracked plug wire case, copper core plug wires, improper shielding somewhere in the stereo wiring, am I missing anything?

oem radio?

From my years doing Auto Sound installations. Whine is usually alternator noise. It is rare for radios to do it themselves, I thought I read that the amp section is separate but bolted to the rest of the radio chassis in the 90 and 91 cars. This whine is usually picked up by a ground loop. If Factory radio, you could get a loop if the radio had lost its chassis ground then it would use the ground from the antenna for the radio, or the reverse Radio ground and the antenna is not. I would pull the radio and check the Ground. Black Wire in white plug. and with meter check the outer connection on the antenna lead for ground. If these check out, run test wire from negative side of car battery and attach it to the radio chassis. If the noise goes away there is a difference in ground potential between the factory radio ground lead and true battery ground. You can measure the resistance between the wire you ran and the factory lead, it should read very low close to 0. If this resistance is high enough it will crate a ground loop pulling in the noise.

oem radio?

Yes original radio, just started doing this a few weeks ago. Needs another radio since I got it 2 yrs ago, amo ng for 1 rear speaker and volume control not even, touch it sound blasts or quiet, hard to find a listening level

Mine was caused by a loose negative ground strap at the battery. It got worse to the point where the headlights would dim when the brakes were applied. New connector at the battery cable & a new battery solved it.