T660 emissions stop switch?

[Chamberpains]

   

I just bought this truck (2010 Kenworth T660 cm871 590,000 miles) I've been pulling it apart and getting it ready to be put in service. I noticed the pictured switch in the truck. I have an idea what it does but not positive. Owners manual didn't come with the truck. Im supposing its a toggle to turn off the regen cycle. I have reason to believe this switch has never been in the up/on position. I pulled the Intake manifold off yesterday and saw inside the head was really clean and had very little soot. Its the factory original head. Today I dropped the DPF to get it ready for a demandate and all I found inside of it was the metal pre screen (its getting torched out today) there is zero material inside the DPF filter. I believe there hasn't been any kind of ECM programming done. The file I pulled is just the updated file from the factory original AV10069.26 to the current file in it AV10228.05. I dont have an original Incal file to do a comparison but I don't believe its been altered. I'll know more once I get hooked up with Mommaburt to ensure things are taken care of properly.
   
My questions would be, what exactly does the switch do? What exactly does the engine do in response if this switch is ran in that position for 100's of thousands of miles? Is there any damage that may have happened by running it this way?

Also as an aside, I found the impeller from a turbo in the DPF canister. I know they replaced the turbo 80,000 miles ago (probably for the impeller shooting out of it) with a crap aftermarket turbo from New Jersey. Which I have the maintenance records that state that crap turbo was then warrantied again 3 months later. I have a YTS turbo coming to replace this Turbo Solutions garbage. I've been arm pit deep in cleaning burnt oil out of the intake piping and CAC from 2 failed turbos. There's nothing showing wrong with the aftermarket turbo but there is no way im taking a chance with it.