could the dumpvalve, u can proberly hear the clicking from the engine bay coming from the hole in the blukhead where your speedeo cable comes through, or the clicking could be the speedeo cable itself, but this doesnt lead to your problem

its more than likely an air leak somewhere, do u run a boost gauge?, check the vacumm pipe going to it, has slipped off a bit?, or chaffed on the bluk head?

or could be pinking under load, but this also dont lead to your air leak noise