Exhaust fumes in cabin when A/C on recirculate

I have been running with a gutted Toyota OEM catalytic.

I replaced all exhaust related gaskets from the manifold header gasket on the backside of the block and both donuts. All pipe and muffler are in good shape. I also added an extension to the rear outlet pipe off the backside of the muffler to get the final outlet mouth behind the bumper / wind catch zones.

I added weather stripping to the rear hatch to improve its sealing and also sealed most/all of the rear trunk areas sheet metal base under the cargo storage / spare wheel / etc. with urethane expanding foam, glue, etc.

Despite my best efforts, it seems like putting the AC on recirc yields fumes in cabin fairly consistently. However, putting it on the exterior intake option yields mostly good enough results I can drive it daily, however they do still come and go in the cab a bit, even on that mode.

What can I do to get to the bottom of this? I am over pulling this thing apart over and over for minimal to no results.

 

I don't disagree, but it seems like even riding with the from windows down draws it in pretty bad. I really think it's just external air wash finding ways into the car through all the holes and leaky bits and pieces, but seems strange coming from so far forward.

I've already got one in the garage... just wanted to sort out the root of the problem rather than mask it before installing the aftermarket cat.

If i replace the cat now, the fumes will still be making their way into the cab, I just won't be able to notice them. imo

 

no

that, we can both agree on

ahahahhahahahahaaaa! that was a good one