I had a similar issue with my 945. In my case, it occurred right after a fillup. Or more exactly, it was strongest right after a fillup. Like you, I suspected something related to the EVAP system. This issue came with the car. Meaning, as the second owner, I never knew the car to not do this, the issue was inherited.

The solution was amazingly simple: the black rubber fuel filler neck seal (seals the cap end of the filler neck to the body of the car behind the hinged flap/cover) had come off the body of the car, leaving a tiny but obviously significant gap. As I inherited this issue, and this is my first car of this type, I didn't know any better. Refitting the seal to the body corrected the issue--it's never returned. Again. my issue presented differently, but I think it's a good place to start.



Not relevant, but the way I discovered the issue is that on that seal (still very visible, as it was butted up against the back of the quarter panel) had two impressions on the RHS, which seemed to line up with the round pegs (again, I'm bad with terms) that keeps the unhinged side of the flap against the inside of the filler recess, and is what keeps the filler door flush with the outside of the quarter panel. My filler door was slightly recessed, and I presumed there was some kind of rubber bumper that fit into the hole in those pegs. I had some extra of those small round bumpers that fit into the license plate bracket, so I put them in the gas door to make the door flush. In trying to find the correct part, I realized there appeared to not be any kind of bumper in those pegs. So I looked at my car more closely and finally realized the seal wasn't on properly. So if your fuel filler door doesn't look right, that could be another sign.

I hope this helps
-Wilson


EDIT: I was so eager to share my story, that I forgot about your p0442 code. My car is OBD1, and I had no code. However, I can't see how my issue would have triggered one. In your case, it seems more likely that it's something else. Perhaps a cracked bit of rubber in the vent near the tank, or possibly a bad fuel cap seal (that's not uncommon). I should clarify that my smell was inside the car, as well as outside. I'm glad I responded though. I'm guessing I'm not the only one who ever had my issue, assuming it happened on it's own, and not the oversight of some mechanic. I know on my car, all of that business is fairly accessible from under the car. I'm sure IRS makes it a little more complicated, but with a flashlight, telescopic mirror, and your favorite coffee or beer, it should be a straightforward job.

2nd EDIT: I'd obviously start with the filler cap seal. If it's dry or cracked, a new seal or cap is a no-brainer. On a different car, I couldn't buy the seal separate of the cap, and was still in the diagnosis stage. This car, a Honda DID present me with a CEL and emissions related code (but no smell, as I recall). Anyway, I removed the seal from the cap, and reinstalled it flipped over. Issue resolved, and I ended up never needing to replace it.