Its not uncommon. You amped the input from the radio so it has amped up any amount of noise that was already there. You probably had the noise before that you could not here but not its loud enough to hear. Some call it feedback. To elimate the noise you would want to check that the CB healthy. Check antenna for SWR. This alone will cause feedback. High SWR will show up as noise. Get the SWR as low as possible. You can sometimes change the noise by relocating the CB antenna away from the AM/FM antenna. Elimating the noise is usually done by fixing the source of the noise.
A secound though is to turn down the gains on the amps you installed as well as make sure all the grounds for the amps are at the same place.
The old klesache you have noise because you have a loud CB. If the mod has been upgraded this will cause extra noise. You might turn down the mike gain some and cut down on the noise. Sometimes a extra lound CB means it will cause extra unwanted noise.
If it was me I would address all of the above to cut down on noise. Hope this helps.