Hi and welcome along. Good luck in your search. I know you’re after a 370z but I have a 350z for sale and it’s a great car. I have re upgraded to a 370z again they’re great cars.
I can't see it popping anytime soon. Although my I think it depends on a lot of things. Mileage being 1 of the biggest factors. Anything over 100,000 miles people seem to run a mile from (pardon the pun)....
My car has high flow cats on and never smelt of petrol. It could be over fuelling. It might have loose bolts. Best get it on a ramp and check it out. As for the eml light would probably be due to the high flow cats. Probably nothing to worry about on that front.