Bill took the words out of my mouth. Sounds like a lifter. Obviously it is impossible to diagnose over the internet but I had a 89 Probe GT that had the 2.2L turbo Mazda engine in it and I had a ticking sound from the valve cover area which turned out to be a lifter. I just changed all of them because once one goes they ususally all go. Do you rev the engine pretty high or shift right at the rev. limit all the time ? If so this will toast hydraulic lifters quicker.