electrical problems - Need Help

88-turbo II. 118k miles. Car starts only after a couple cranks, but that's nothing new. New problem is that when I push down the clutch and disengage the car radio will flicker, suggesting electrical problems, maybe battery problems. When I engage the clutch again and shift to the next gear this stops. Also if I am stopped at a light, switch into neutral and bring the car to a complete stop, the radio will flicker, and the engine will die. If I do the toe-heel brake gas method and give the car about 1000-2000 RPMS while I am stopped, it will not die, and the radio will not flicker. I am thinking this is due to a problem with the battery or the engine in general. Perhaps the negative battery cable?

what do you think>?

Have you gotten an idle voltage reading yet?

It appears that the battery cells are ok. And the alternator is also working fine. There is a difference in the voltage from the battery to the alternator. I am going to try and clean the battery cables which are pretty corroded and also check the wiring for any loss of connections. This appears to be a wiring problem.