I changed the spark plugs and coil packs last spring, I put in a new air filter a month ago.i never had the throttle body or the maf cleaned out, but the rumbling been happening on and off for a week.

so when I start my car it rumbles when it idles and it gets worse as I drive then it smooths out. I have a trouble code p0455 and I know it’s for emissions. I also get a faint exhaust scent inside the car. I have 144000 for mileage on a 99 s80 2.8. Is it worth the repair?