When installing an after market nav system like Kenwood or Pioneer, dose it mean that the original features that comes with factory nav system will be lost, like the auto volume adjustment and the steering while control.

 

No, you'll just have to buy the adapter that has to be wired into the steering wheel and the unit. I installed a D3 and still have full steering wheel controls, etc...

I used the PAC adapter kit. I'm pretty sure Peripheral makes them as well...atleast I think that's the name lol

 

That good.
From where you got the PAC adapter kit for the steering while control, and what about the volume auto-adjustment?

 

just do a search on google for pac swi-ps or if u want i can sell u one. that is the steering wheel interface that you need. as far as the other part i dont believe there is an interface for that, but i could be wrong.

 

I'm not sure about auto volume adjustment, I never use that.