any gmc bose experts?

I just bought a 03 gmc sierra ext cab and it has a bose system in it. The radio seems to work correctly except the output is really low. First off the RPO codes show that my truck has the "standard" bose system. I have done a lot of digging and think I am headed in the right direction but still need some help. I am not sure that it has the correct wiring harness in it. The basics of what I have figured out is that my radio is programed to output a low level signal through what would normally be the regular speaker outputs. This signal is sent to the bose amp and then to the speakers. There is also supposed to be a pink amp turn on wire which my harness going into the radio does not have. also there is a connector halfway between the radio and the amp harness that has the pink and a few other wires going towards the amp but the connector coming from the radio (i think) does not have the pink turn on wire or the several others. ALSO the wiring harness further down for the amp has a gmc delco label on it dated 2005 and my truck is a 2003 but it does appear to be the correct harness except for an extra connector which is for a rear control I assume. I beleive the radio harness was replaced with a non bose harness because of the low volume (from the bose programed radio) going straight to the speakers instead of to the amp as it should. Oh and one other thing that makes me think that is that I can completely disconnect ALL the connectors besides the large connector on the back of the radio and it will still work the same. The big reason I doubt this is because the harness looks factory installed with all the plastic holders and everything in place and it merging into the ac controls wiring as well as it being all taped or wrapped like it comes from the factory. Sorry about being so long winded but I don't see a simple awnser so I included as much detail as possible. This is driving me up the wall.

The chances of the radio harness being replaced and looking like it was factory installed are remote. The output level of the radio is altered when the radio is programmed using GM's TIS2WEB computer system. The programming also dictates how the radio is to turn on the amp among other things. If you can, post all the RPO codes from your truck that begin with a "U" and with a "Y". Is your Sierra a Denali model too? This makes a difference. Try disconnecting the radio and see if you still hear a chime when you turn on the headlight switch with the igntion turned off. The fact that the amp has a date code of 2005 means it has been replaced with an updated model. Post your results and I will be able to help.sparky

I just while typint this went back out there and looked at it some more and the radio connector c1 24 pin is the exact same as the intermediate connector from the amp harness and I decided to swap them and it works correctly now except the rear speakers dont work now but that will be the next step. Thanks for the help even if it didn't directly help it did make me go look again at the radio connector when I went to disconnect it. Now on to the hvac controls LOL