Lindsay vw is the most friendly of all. As well as stohlman's in tysons corner, i believe you have to ask for john or josh for appoinment there. I got my car at rosenthal vw in fairfax, still had my warranty when my mk6 was stage 1 but only warranty covers parts that doesnt have to do with tune itself.
Edit: directly to forzagti
Thanks for the info!
Seems that VW Fairfax is OK with Stage 1+ mods, at least that's my experience yesterday. I dealt with Leo K. (a service adviser)