huh?
parasitic energy drains, like computer memory, clock, stuff like that, ought to drain a total of about 50 milliamps or less. if you've got more than that going out, try pulling the fuses one by one, and measuring the difference in draw each time (take notes, by the way). When you're done, you will be able to isolate the circuit(s) that's causing the excessive draw.
the capacitor on your radio should be attached to the antenna circuit, not the power. its purpose is to filter out emi/rfi noise. that shouldn't have any effect at all. in fact, since capacitors store up energy until the pressure is great enough to overcome the strength of the internal insulator (dielectric), a capacitor would tend to have the effect of suppressing the draw, not encouraging leakage.
Shut the engine off and leave it off while you go have a beer before you make the tests, so that you can eliminate the effect of devices that stay on for some period of time after the engine's turned off.
