They ARE NOT backfires, they are after fires. Unspent fuel burning off in the exhaust from using a BOV (and particularly a bad one at that). The only way to fix it is either get a better brand, or put the stock on back on.
After fires because now you're running rich between shifts. The only way to stop it is to take it off. Not a huge deal that it's doing it. What I would be worried about is that TXS H-line valves tend to leak.
When it wooshes, that atmospheric BOV is getting rid of fresh/cool/compressed air that the engine is expecting to be there. Your ECU is dumping extra fuel into your engine which would normally mix with that air and since there's no air to mix with it, it's igniting much later than it should (when it hits the air in your exhaust pipe). I'd also recommend putting your stock bpv (or another fully recirculating unit) back on.
I'm sorry, please research stuff you spend money on.
Take it off and sell it. (dislike)
Like times 100, yes please before you tinker around with something that you don't know please research. Take it off, the stock unit is perfectly fine. If your just looking for a "cool" noise than get a catback or something..
When it works, that atmospheric BOV gets rid of fresh and compressed air that the engine is expecting to be there. The ECU has dumped extra fuel into your engine that normally mix up the air. If fire occurs you can run between the shifts.