[Cunningr]

I take it you have a factory 4 channel amp?

Asuming all you did was replace hu and used an adptor kit you should check your wiring connections again.

For the factory amp you need to use rca out of hu, the factoryamp wont take line level input signal.

I am in the process of doing a complete ugrade, myself. I tried 5he 6 channl amp route and is ok, and easy mod but better off with complete system upgrade.