i have been having a similar problem with mine as well, and believe it or not i took out my jet valves and two of mine are missing the valve faces,

when ever my truck got in a low power fit it also had a ticking at the same time, but mine was deff the engine.

so i happened to pull off the valve cover when it was in one of its fits and the jet valve was stuck compressed down and that was the crazy ticking was there was about a inch of space between the jet valve and the lash adjuster.

now i am stumped cause i am having a hell of a hard time to find jet valve eliminators in canada