Need some help will clear corners
Brandon (af-s4-driver) and Zach (themoneypit) have both done this mod with luck. Talk to them.
chip: Just about whatever you want. REVO, APR, and GIAC all have great reputations. Taylor from SE Tuning sells REVO.
BOV: the 710N is the bypass valve found on the 225HP TT. It effectively replaces the stock bypass valves on both S4's and A4's. Purchase a pair of those and don't look back.
wastegates: KKK turbos use internal wastegates. Unless you are having problems with yours (and if you are, upgrade the turbos while you're at it), keep 'em stock. To be honest, I'm not even sure if there is an "upgrade" for the wastegate.