[phantomrt]

I have seen bearings get eaten up slowly to the point where the bearing clearance to the crankshaft is huge--like .05" or so and you get a light knocking, and that beating the bearing takes when the crank pin rattles around in there is enough to deform the bearing enough where it becomes loose and can spin around in the rod a bit. But if that bearing welds itself to the crank pin, (true meaning of a SPUN bearing if you want to be technical) the connecting rod is destroyed instantly and there is nothing quiet about the engine after that. However, I really believe that you can relax over that being an issue right now.

If in doubt, remove the oil pan and if you have bearing issues, it will be obvious by looking at the glitter inside. Also, if you reach up and try to move the connecting rods perpendicular to the crankshaft centerline, you will be able to FEEL play in there if there is a problem. If you cannot feel the play, you cannot hear it. It is normal to feel a VERY slight amount of play when twisting the rods though. Most people wouldn't notice that kind of play. It is almost not even worth mentioning.

To further describe such an exhaust leak noise... at normal cruise, you basically cannot hear it, or maybe you can. Ease on the gas pedal a bit and then you hear the "ticking" noise start or get worse.

I am guessing either a missing gasket, a doubled-up gasket (where the old one wasn't removed), a re-used gasket, or a bolt or two is just not tight is the cause. Over-torquing sounds doubtful unless it was to the point where the bolt was at the verge of breaking and then it finally snapped later on when a few thermal cycles got to it. I predict that the leak is caused by the EGR tube, where the header bolts to the cylinder head, or where the downpipes attach to the headers/turbos. Possibly between the turbo and the header?

And yes, it could be a cracked header. There are aftermarket headers for cars ranging from a Model T to a brand new Nissan GTR. Some are total garbage. A child could have made a better quality header than some that are out there.

Having a dyno on hand would probably make finding this exhaust leak MUCH easier... put the engine under a constant load and poke around with a stethoscope until it is found.