Ticking noise on acceleration?

[rkr]

Well, my 02 burb with 6.0 engine has a ticking noise on acceleration that's starting to bug me. It happens only on acceleration from low rpms and does not happen all the time. It almost sounds like pre ignition on one or two cylinders but the knock sensor says everything is fine when I use my scanner. There's good oil in the engine and everything should be OK maintenance vice. What could be the cause of that irritating noise? It's really hard to diagnose since it happens only on acceleration, listening at idle reveals nothing.

[rkr]

While inspecting the engine I found that the rearmost exhaust manifold bolt on driver's side had broken. Luckily there's a stump that's almost flush with the manifold surface so I should be able to take it out. Now is there any reason not to use grade 8.8 bolts from HW store instead of those GM bolts that have a tendency to snap off?