I'm having trouble with my sound randomly switching from the rear speakers to having a ton of sound in both front and back. I noticed all of the sound comes when I go around a turn sometimes. It will keep switching back and forth and eventually stop at some medium. It does not do it everyday, but enough to drive me crazy.

Probably your speakers arent screwed on..thus flying free back and forth everytime u turn.

Nah....I think either the HU is bad....or it sounds like something is touching ground when u turn..probably rotted speaker wires.

To check the speaker wires, should I just unscrew the 4x6's and lift them to check the wires? And is it possible to fix the HU?

It is possible to fix the HU...but unless u really love the stock look I'd just go aftermarket (in case that was the problem)
And the speaker wire could be rotted anywhere....ur best bet would be to hook up another radio (borrow it from a friend or something) n if its not that run some new wiring...

imma say the wires arent crimp/saudered together, i had the same prob on mine. damn speaker wires were just held together with tape

Ok, I'll check these out today. Also, I noticed there should be a plastic stud similar - if not identical to - the one that helps stabilizes the ECU that mounts into that car that I don't have. I saw the hole for it behind the radio and the spot that it would connect to on the back on the actual radio. Anyone know where to get one?