From an article on the Toyota - BMW Supra/M4 collaboration,
"...BMW couldn’t believe how extensive some of our quality and efficiency studies were as parts came into shape one by one. We would take every bit down to a fastener or rivet, and put it through our stringent quality control and a dozen other testing, we’d ship thousands of parts back to Japan for analysis. That is normal to us."
http://club4ag.com/chief-engineer-tetsuya-tada-reveals-the-a...