it definitely sounds like the ignition circuit is causing interference with the radio. did you do a range check?
why was the ign replaced?
is the ign module, it's battery and all it's associated wiring all located and routed completely away from all wiring for the radio?
(like all forward of the firewall?)
is the radio's airborne battery fully charged?
I have heard of cases where not having the spark plug wire fully seated (or simply loose) can cause interference issues, but I have not witnessed them personally.
(this is what Michael is referring to, you'd add a hose clamp clamping the spark plug wire's rubber boot to the spark plug itself)