I was getting noise from my engine area and thought it might be where the down pipe connects to the exhaust manifold. So I attempted to tighten the bolts but they appeared to be tight. I bought new bolts, M10-1.5 x 45mm, coated them with a little copper anti seize and torque them down to 23 foot pounds and guess what, noise is gone. Apparently the old bolts were incapable of torquing to the right value and tightening the exhaust at the same time. Just a thought.