I, too, am having the exact same issue with my 2003 RAV4 with 106,000 miles on it. Had the misfire, took vehicle to mechanic, who replaced one of the coils and all the spark plugs, and changed the oil. Vehicle ran fine after, but started showing P0420 and P0430 several days later.
Went back to my mechanic, who felt it was unlikely that I had actually damaged anything in the limited amount of low-speed driving I did after the misfire (abt 30 miles.) As I live in an area where it's very difficult to drive far enough or fast enough to properly reset things (an island off the Massachusetts coast), he felt that my impending drive to my second home in Florida (abt 1400 miles) might well resolve the problem.The vehicle ran fine on the drive down and got the same gas mileage it always has (abt 24-25 mpg. ) Sadly, it has not resolved the code problem, which will have to be taken care off to pass Mass. inspection when I get back. It also shows the evaporative system as "not ready."
I was wondering if anyone who posted on this issue found resolution, or if anyone has any thoughts on the best way to proceed from here. I'm hoping to avoid a situation resulting in the ongoing random replacement of expensive parts. Thanks in advance.