Looks like Magnaflow will be releasing a 4" turbo-back for the LLY soon.

http://www.magnaflow.com/02product/shopdisplayproducts.asp?SID=4Chevrolet&zone=Diesel&id=231&cat=Duramax

I have emailed them for a release date but no response from them yet...

Has anyone heard when these might be out?

Thanks,
-Allen