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One thing to look at.

Have a shop with a modern charging system tester look at your alternator's output.

They will check it for maximum power under load and look at ripple in the DC output. If there is a lot of ripple and the peak power is down the alternator could have one bad rectifier diode. It will still keep the vehicle charged unless you sit at a red light with the defrogger, wipers and lights on.

The ripple will show up as whine in your radio and give you a nasty hangover.

so let me see if I am looking at this correctly. on this home made filter, there is a black wire coming out (that goes to the positive side of the battery) and the 2 ends of the red line are inline from where your 12+ source is to the radio?

No, not quite right. One of those red wires goes to the (+) side of the battery, the other red wire goes to your radio. The black wire (-) goes to the negative side of the battery, or the vehicle's ground (assuming that the the thing is a negative ground to start with).
- 'Doc

Just like it says under the last photo: the red lead connected to the capacitor goes to the radio. The other red lead goes to the battery. The black lead goes to ground. Keep connections at the radio end as short as is practicable.

__________________
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73 de K7KBN

DUH!!! was late last night when I was reading it. now that I look at it, it makes perfect sense!