I just use TCW3 two stroke oil every onece in awhile in my cummins, works great and definetly makes a diff, I still havent used anything else besides two stroke oil only because I have basically an ulimited amount of two stroke oil.
Amsoil Diesel Fuel Additive is formulated perfectly for Adding lubricity. With the new fuel upcoming, Amsoil is releasing some new additives next month that will focus mailnly on giving fuel more lubricating properties.
Stanadyne, Amsoil, or any other cetane booster and or fuel system cleaner that DOESNT contain alcohol is what you would want. I dont know if chevy is, but ford is even offering a ford cetane booster, although im sure its actually made by someone else...
stanadyne has a lubricity formula, they should have their redesigned all season performance formula on shelves soon, they are reformulating for ulsd. i use stanadyne its not always easy to find but works well and chevy does recommend it for use. i know people who use fppf lubricity plus fuel power and add fppf cetane improver. fppf also makes a product called total power.
I would highly recomend Bi-Tron Fuel Conditioner. It cleans, lubricates, and helps the fuel burn better. I have ran it in my truck for the last year and the best part about is the exhast is not a black which makes cleaning my truck a lot easier!
You'll find hours of reading about ULSD (S15), if you do a search for "ULSD fuel". I use Dogpile search engine and just received 75 website to read. Additives are un-needed with ULSD, is the response from most all diesel engine mfgrs.