You don't have to. Lots of high power turbo cars run SD stand alones and still recurculate.

But I'm saYing that people go SD just to vent to the atmosphere and get that sound.. yet I recurculate with a maf and still get a loud boV sound.

11.45@125,
stock bottom end 6bolt 2g head.
272 hks cams.
Holset hx35
Backyard biult!!