Audio Systems: Factory radio help, rca outputs, channel amp

Question
Hello i just have a few questions if you would be willing to answer them.  I installed the new pioneer 4 channel amp to my factory system in my ford f250 and used that purple scosche box to convert to rca outputs.  Everything works but the left two speakers don't sound right.  there not as loud.  I have reversed the wires doesn't help.  I have switched left to right to see if it would switch to the right side and still stayed on the left.  I used the factory wires so i bypassed the factory wiring and went from amp to directly to the speakers and no difference.  I powered the amp from the left battery didn't know if that would make a difference.  What should i do?

Answer
If you went from the radio directly to the speakers and then swapped sides and it is the same that answers your question, It's NOT the amp, (that's out of the system) and it's not the radio (as you swapped L & R channels,)so it must be it's the speakers themselves or their wiring, try swapping a left with the right. Which battery you use doesn't matter, you should use a separate battery and a split charge relay anyway for a large amp.
Regards Peter