Re the radio noise increasing with revs , following
all at your own risk and in conjunction with your lame.
If it was ok with an existing radio and only started once you swapped radios I'd start with the radio install.
I'd do the following one at a time to see what fixes it. Electrical noise can be a challenge to find.
I'd run the radio on a gel cell and see it the noise is still there, this might indicate it's getting in the dc / power supply to the radio.
if noise goes away
I'd try making sure all my grounds at the radio are connected at the same clean metal point not on the aircraft frame ; radio, aerial, dc supply and headset and ptt if practical.
if you cant help that it is connected to the frame then so be it.
Then I'd make sure the above radio ground point is connected to the engine frame at the same location as all the other grounds from all the other equipment.
So to write it out in a 2 d wiring diagram of the aircraft electrical grounds it would look like a star with a central point with all circuits and sub circuits going to that point.
This might help reduce ground loops or potential voltage differences, frame & engine electrolytic corrosion.
I'd then check the positive power supply to the radio was not wired to the same source as the ignition system
I'd make sure my ignition system, starter earth / negative lead and engine grounds are to that same point.
if the noise was still there when running on the gel cell
I'd check my spark plug leads with an ohm meter then swap out my spark plugs.
I'd put suppressors on the ignition system primary then secondary.
I'd shield and ground the ignition secondary as best I could [fine chicken wire mesh over the outside of the ignition coils hollow braided over the spark plugs and leads all grounded to one point. [some older Bmw cop bikes had metal shields over the coils to allow better radio reception.}
fta 550 aa for about a year now , yet to use it for real , a big hand held but way easier to read in a hurry.
Kind regards Donald