By the way, ARP and every other bolt stretches as it is supposed to in order to achieve proper clamp load in a threaded fastener joint. If you go too far, you exceed the elastic limits of the fastener and you approach the yield point. Most modern cars use head bolts that are into the yield curve of the bolt so that is why they are considered "one time use" only. It requires a sophisticated fastening tool to accurately know when you are approaching the yield point (they detect change in slope of the torque vs degrees of rotation curve during the tightening cycle).
Some very good info here:
http://www.boltscience.com/pages/tighten.htm