you said the stock radio was a monsoon, did you remove the monsoon amp, or is is still hooked up? I had a similar problem a few years back, the battery would go dead in a few hours. Much cussing and tracing later I figured out the amp was not powering down. Pulled the fuse and all was good. Got tired of that, figured out which wire went to the amp and put a switch on it. Haven't had the problem since. Mine is an 03 and the amp is in the left rear corner behind the plastic.