It is a good idea to upgrade the BPV/DV because the chip might cause your OEM BPV/DV to fail and leak boost.
Quick breakdown for you:
The difference between a BPV (or DV) and a BOV?
A BPV (or DV) is a Bypass Valve (or Diverter Valve).
A BOV is a Blow Off Valve.
A BOV vents excess pressure generated between shifts to the atmosphere, thus purging the air OUT of the intake tract. A BPV recirculates the excess pressure and keeps it IN the intake tract.
For Audi turbo systems, utilizing a BOV is NOT a good idea as it will cause a rich condition (i.e. less air to fuel ratio) and cause damage to the cat, soot on the exhaust pipes, occasional misfiring due to the loss of the purged air, etc.
Here is a current list of commercial DV's available worldwide:
AmD Viper = Polished chrome version of Bailey DV with AmD logo, $$$(see "Bailey" below)
Bailey = Probably the most popular, serviceable, $$$
Evolution Motorsports = Cosmetic (4 color choices), not serviceable, $$
Forge = Large (may have fitment problems), serviceable, $$
Forge Race = Larger than others (see above), adjustable, serviceable, $$$
Hyperboost = Cosmetic package, not serviceable, $$
Hyperboost Adjustable = New, cosmetic package, may not fit S4, adjustable preload, not serviceable, $$$
Hyperboost HX = Newest, very cosmetic package, new internals, not serviceable, $$$
OE Bosch TT 710N = Basic, popular & low-budget upgrade, maintains stock look, not serviceable, Audi part# 06A-145-710-N, $
OE Bosch Sport 110 = MTM upgrade, same as 710N with "better" internals, not serviceable, $$
$ = under $50 USD
$$ = $50 - $150 USD
$$$ = Over $150 USD
