Or the regulator inside the alternator is a source of RF.
There are just too many other potential reasons to but only
blame a computer or instrument cluster.

Cars do not come from the factory with static. Number one
reason for static would not be cured with RF choke.
Furthermore, the RF choke would not identify noise entering
due to bad ground. Better is to first learn what has been
changed - to have created this problem. To have better help
from the newsgroup, the OP must provide model, year, what is
and is not original in the vehicle, what has changed, etc. By
rationing facts, his responses can only be speculative - not
very helpful.

TimPerry wrote:
the cars onboard computer or instrument cluster is generating RF.

"fish" around with a portable radio to localize the problem.

recheck the car antenna system. try a RF choke on the DC power wire(s)