Originally Posted by Jeff@TopGearSolutions
There are only a few ticking sounds that are "normal" on this car.
1) Injector ticking, they make noise, it is normal.
2) Fuel pressure release valve, also sounds like injectors ticking. If you rev the engine it will go away and return.
Any other rattles near the exhaust are usually wastegate rattle. It is normal in the sense that it is a common problem on these cars. Bring it to the dealer if you are under warranty and stock.
Any other excessive ticking noises may be valve train noise. Go to dealer if it is a concern but they will likely do nothing unless its excessively loud or throwing codes.
The e36 and e46 problem were notorious for needing valve timing adjustments as early as 20,000 miles, but the N54 doesn't have that problem.
Happens to my car as well. I also figured it to be something fuel related, and probably not much of an issue. I had a Mazdaspeed6 (also DI) that made a similar noise. Not anything I'm worried about.