tick noise

Check your spark plugs...it could be one backing out, and make sure when you check that the engine is cold, you dont want any stripped threads, there is only like 4 in PI heads!!!

I had a similar problem, couldnt hear it from inside the car w/ the windows up, but it was audible w/ windows down or from outside the car at idle. I had a timing chain tensioner fail which allowed the timing chain to slap against the guide. If your ticking noise sounds like metal to plastic (loud tick but not metal to metal) then I'd look into that. A little costly of a fix but better than a bottom end going out. Next time you star the car and the noise re-occurs, grab a screwdriver and try to isolate it to the timing cover, also would hear it most from the valve covers. If its more audible at the bottom end I would say its not your timing chain tensioner.

*edit*

I believe 03+ heads have more threads in for sparkplugs. Still may be your problem though.