So I've noticed it more lately.. it's always been on and off.. but maybe I just get the wrong gust of wind. A lot of the time when the car is stopped and in my mind the wind is the right way, I will get exhaust smell in the cabin. It does get kind of strong if I'm stuck at a light really long. I don't notice the smell itself when I'm outside the car, but in a closed cabin can make a lot of difference.

I have had a few thoughts.. but nothing solid. 1) I know there are trunk vents .. but I still have the flaps on them so I doubt the air/fumes are getting in that far that fast. 2) I thought maybe the cabin air filters were off.. but it would probably have to be really out of alignment wouldn't they to let air from the engine bay in? 3) as part of 2 would I have to have a large exhaust manifold crack or leak?

Some post had mentioned a breather valve, which I have not really had much luck in finding info on.

To be clear it's exhaust fumes, not burning oil.. which I smelt a little bit when my front oil cooler gasket went.

May be unrelated.. but relevant. I had my intakes walnut blasted a few months ago. I have also noticed that on occasion my car doesn't start up properly like the fuel rail/injector etc didn't have enough pressure and leaked. If I put my key in and hit the start button and wait even just a few seconds it'll be fine.

Would/could this be related? And.. if anything is there a way to test for this? Car runs otherwise tip top, from idle to WOT acceleration, so it's more of a nuisance at this point.