I have a 06 wrx wagon, automatic, no turbo guage, 115k miles, stock, maintained well.
I noticed this last week that the turbo is not kicking in when it usually does (around 4000rpm?), and not at all. Service engine light is not on. I haven't noticed any ongoing unusual noises. Only odd thing I can think of is a couple days ago I heard a sound under the car that sounded like I ran something over in the street - like a twig or something small that kicked up under the car - but when I looked in the rear view I didn't see anything. I wasn't in turbo mode, just at an average 30mph cruising speed. Also hadn't used the turbo for a while before that. In fact I may have noticed the lack of turbo before that incident. As I said, I haven't noticed anything else out of the ordinary.
How can I tell if the "turbo is blown" and needs full replacing or if it is something else?
Would the service engine light go on?
Any tell tale signs under the hood? I am a relative noob.
Recently replaced power steering belt.
Any advice on stearing away from getting screwed if I take it in to be checked out and/or fixed?