Just a warning that you sometimes get exactly what you paid for!
A year ago I was doing a bunch of regular maintenance on my 2007 X3 3.0si. I figured since I had heard of so many vanos solenoid failures I would just swap them out since I was getting dirty anyway. I bought cheap Chinese ones for around $30 each. A month later I started getting engine lights and a stumble after an hour or so of driving. The code was exhaust vanos.

Luckily I am a pack rat. Today I cleaned one of the old ones up and swapped the exhaust vanos solenoid... X3 is once again so smooth that you have to look at the tach to know it is running. Code is not coming back.

Sometimes cheap is NOT a deal.
I fully expect to have to put the old intake vanos solenoid back in before too long but it's not even a 10 minute job so I will await the failure before bothering. LOL