Socalgal

I may have actually made some headway with this fellas.

Thanks for all the ideas and I'll address these first.

My exhaust manifold is a very high end jdm unit made by wisesquare. It's extremely thick, gusseted everywhere, and was just re-machined at a good machine shop to confirm the flanges weren't warped. While they were at it I had the elbow and downpipe flanges machined and my hks turbo exhaust housing checked. Everything has new gaskets, studs, and nuts and has been triple checked by myself and a few trusted shops and I'm sure all that stuff is good right now. The best way I know to check is with a stethoscope with a metal end. We've also confirmed to the best of our abilities that there is no cracks as well.

Jr__Ss- The hvac intake ducts are on the cowl correct? I would assume they are open when using the heat or ac without the recirculating function on but again there is no exhaust leak in the engine bay to be pushed in there and there is also a pretty new seal in-between the hood's backside and plastic cowl. I also had that all apart lately looking for a ring I lost when doing the exhaust gaskets and everything is mint. On top of all this if the windows are up I get no fumes with any mode threw the vents in the car.*

I know all my transmission area boots are intact but I took that area apart again and the metal Both of the chassis and the ring that holds the boot to it were not perfect. I spent quite a while finessing things back to perfect and reassembled yesterday. I'm not sure this changed anything but it was something to do.

The cabin pressure equalizer box snaps in at the top and has two bolts that hold the bottom. The top was not snapped in and it was kinda hanging quite far out. I had taken the box out to do a closer inspection of the flaps and when reinstalling I heard the top snap into place and it all makes since now. I'm sure I'm not the first person to think that was a very convenient place for antifreeze and oil lol. All my fault.

Test rides went well last night. It used to be that the second I cracked any window or sunroof you'd get the faint smell of exhaust and I'd start yawning within a min and feeling what I've come to associate with monoxide.

I went like 25 highway miles trying all the different windows and hvac controls last night and no yawning.

Also the way air moves threw out the car with windows opened seems a lot less violent at highway speeds.

I think the aerodynamics of this vehicle (or pretty much any for that matter) might allow air and therefore a bit of the exhaust to be swirled, or sucked back under the bumper and with that box not able to do its job as a one way valve (essentially) it could've been sucked back in there.

I've not had a chance to put many miles on it yet but this definitely helped if not fixed it all together. My tail lights also do not seem to have any of the sealant around them so that's next.