https://www.zshackperformance.com/blogs/news/arp2000-head-studs-the-truth-about-them From Facebook and a friend in the states I've quiried at times. The above link carries findings regarding possible wrong branding of headstuds. Chromoly instead of genuine ARP2000. Also reasoning why L19 are not necessarily the go to strongest. The washers is a fairly common known issue now so no surprise it's encorporated. I think I may be checking mine next time car is in shop (built 5 years ago in september) Sadly I can't check packaging or model numbers now. Anyone readying a build it may be worthwhile to check.