NorCal Dynamics has the best customer service I have ever received from a parts retailer! I recently purchased a MHD FLEXFUEL ANALYZER KIT for my 2013 135i from NorCal Dynamics. Unfortunately, I ordered the wrong kit as I was given bad intel by an MHD employee. Needleless to say, the incorrect kit arrived. After figuring out which kit I actually needed (Open Wire for N55 E series), I reached out to Jack at NorCal Dynamics via email to see what could be done about exchanging the incorrect kit for the correct kit. I was expecting the usual wait time that comes with sending email from experiences with other retailers, resulting in my car sitting on the shop lift until I heard something back. However, to my surprise, within minutes of sending the email, Jack went from the email to picking up the phone and calling me to get the situation figured out. He was polite, professional, and understanding of the situation. He had the correct kit ordered and shipped out within 24 hours, and allowed me to send back the incorrect kit for no additional charge (other than restocking fee which is fine). I hope more parts retailers can mimic Jack's process when it comes to customer service. No having to wait 3-5 business days for an email response and an immediate phone call to resolve the issue, was far beyond my expectations. If you need anything for your BMW, make sure to use Jack at NorCal Dynamics, as you can trust any issue or problem you encounter will be quickly resolved and any downtime for your car, will be significantly reduced.