There are no shortage of 2$ items that when they go, they go big time. In this case, the rail didn't fail, it was killed by the stretched timing chain (didn't you pay your mechanic a lot of money to check it often?).
This is one big difference between a benz and a chevy. The mercedes engineers of yore that designed your engine assumed that mechanics are "properly" trained and that owners do what they're told to in the owner's manual. Chevy engineers have assumed that the car will have an uneducated owner and/or mechanic inflict their will upon the car at least once, if not always. Something akin to my mother driving and my dad doing the tuneups.