' 94 Maxima Light Tapping All Sps

I am having a problem with my '94 Maxima. There is an intermitten light tapping heard at all driving speeds and seems to follow the RPM's. It does not seem to lose power just that annoying tapping from the engine area. It was suggested the timing belt, EGR vlvor injectors. Before I go to all the expense, is there anybody here who have experienced that problem and how can I verify this problem.