I have a 99 gt with the mach 460 system. It had a cheap aftermarket head unit and I noticed the door speakers, which I think are subs weren't making any sound at all. I just installed a new head unit hoping that the cheap one may have just bypassed these speakers but they still have no sound. I've checked all the wiring behind the HU and the wiring to the amplifiers and nothing looks like its been tampered with. I only checked the 2 amplifiers in the trunk area, I don't remember if the 99's had the 3 amp set up. Anyone have any ideas?