Ok so I got a 2005 Altima 3.5l with 200,000 miles on it. It's lacking serious power. Threw a multiple miss fire and bank 2 oxygen sensor 2 downstream code. I replaced all coils, plugs, cam sensors, and bank 2 down stream sensor. It runs better, but it still is lacking serious power. It'll barely get up to 70mph and after awhile cruising itll get worse. Its not burning oil, so i dont think a compression test on the cylinders is necessary. It started doing it a couple months ago, but it would be fine in town, it would just start acting up if you went to upper RPMS them is would stay running crappy after that. I'm getting about 10mpg which is horrible. I dont get why its not throwing me an obvious code. Not sure what else to start replacing. ANY help would be wonderful! Thanks.