Looks normal to me having been in there for 8 months. They just look like they've been in for awhile and are due for a changing. As long as you're not seeing really white or really black, i.e too lean or too rich respectively.
As far as the sound, sometimes it could be the simplest of things. Are you sure you're just not hearing the wastegate dumping into the atmosphere?? What's your a/f gauge and EGTs reading at WOT when you feel the power loss and hear the popping sound?

Patrick