Yes, 90 degrees is not desirable for gas flow turbulence but better than not having it. But it's not just the flow of gasses that is important in performance exhausts: ... There is the pressure wave which travels extremely fast (very much faster than the gasses or sound waves) which is significant in assisting with gas scaveging from the cyclnder ... IF it is at the correct tuned length. We assume they got it right.

Cheers, Richard
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09 America, Staintune Pipes, K&N, Breathe, Hagon Nitros, AI & O2 removed, tune 20184 (modified), MTX-L a/f gauge