The vid demonstrates the scavenging operation of the X-pipe when only one side is moving exhaust gasses (out of phase), this will ONLY happen thru the RPM/throttle position/load range with equal length tubing upstream. The X5 has about 2' more exhaust length from the left cyl bank to the X-pipe vs the right cyl bank, this will cause some RPM/throttle position/loads to deliver the pulses in phase.

I'm all for everyone modding to personal taste, I just point out the flaw when it's passed off as a "performance enhancing mod".

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'03 X5 4.4 Sport, last of the M62s (8-03 build date)
I believe in deadication to craftmanship in a world of mediocrity!