OP - is this your daily? I sure hope not. Since you posted already that it sounds like its coming from the front cover focus your efforts there. If it pulls strong under normal situations and just has that odd tick coming from the front cover avoid throwing other variables at the situation. Your next step should be to take a look at whats behind the upper and lower cover. Timing sets are not cheap but they are good insurance for the engine in the long run.

Good luck to you.