Long story short, last year replaces thermostat, 10 months later (2 months ago) SES light comes on low engine temp and both cats bad. Thermostat replaced by Infiniti (still under 1 year warranty) but now have issues with the cats. After researching in the forums I did 2 things: 1 - changed the gas cap and 2 - sourced some new to me used OEM cats. Funnily enough since I got the replacement cats the SESlight hasn't gone on again. The only other thing I have done was fill up with Top Tier gas, 3 different stations/brands, better detergent package. Checked for codes, only found a pending for 1 cat bad.
Car passed inspection/emissions in NJ.

Is it possible the "better" gas limped me through.