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Ok, here's the deal with bolt torques. They basically set the preload on the bolt, but are extremely dependent on the lubrication (friction factor) used on the bolt. In that respect, they are a generally accepted to be within 25% of actual stated value (ie: torquing to stated value will get you within 25% of desired preload). I would suggest not going much over the recommended value, but going a little over wont make a big difference. The issue with over torquing bolts is that if you over torque them (let's say to near the yield point of the bolt), any extra load on the bolt will cause the bolt to yield. Once that load is relaxed, you will basically lose all preload and have a loose bolt.
I have a lot of experience in bolting applications in oil and gas industry. Check out Machinery's Handbook if you want to see the formulas for bolt torque on a bolt.
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