Yes you are fine. BMW uses a vacuum controled valve to open the other tip up during heavier acceleration to reduce backpressure. It also increases the exhaust note. It is design to be quiet while putzing around, and when you get on it it opens both up to allow to motor to breath better and produce a louder exhuast note. If you want the exhaust to be louder and both to be used all the time there are instructions on E90post on how to accomplish this, or you could just Google it.

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'12 E92 M3 ZCP Stage 2 Tune, Exhaust, Test pipes, GTS DCT Software
'07 E70 4.8i
'07 E92 335i FBO+Meth M3 Suspension Swap and much more 505hp 564 lb/ft tq (Sold)
'89 E30 325i (Retired with 230,000 miles )