Your "static" problem most likely is with the radio grounding with the antenna shield. Since the tape player does not have the noise, the power to the radio is fine as in this case alternator power runs tape which generates signal that goes to amplifier and drives speakers. On the other hand, when you use the tuner, the antenna and tuner rather than tape player gives you the signal that goes through the same amplifier that drives the speakers. Thus the noise is on the radio signal. IMHO a Bosch coil will change nothing as the engine runs and the power to the radio is fine, but somewhere the antenna is receiving (noise leaking into antenna signal) the spark discharge noise. Granted, it could be leaking wires-unlikely since they are relatively new and specialized, however, bad antenna mount grounding due to rust on the underside of the mount, bad antenna cable, or bad plug with the shield open, any or all, could be letting the noise into the radio signal. An easy test would be plug an another antenna into the radio and ground the mount to see what noise level you get. Then you can also move the antenna to see if the noise level increases based on position.
Post back and if this is not the source, then the next step is really checking the wires and coil for an open wire or wire not fully seated.