Noticed misfires from my ody with 191k. Throwing codes like no other. Self diagnosed myself and bought a ignition coil $40, cleaned egr, all giving same code. Took it to my friends shop he diagnosed to adjust the valves. $250 later no more codes runs like it should and gas mileage back to normal. Btw, this is a DIY but you will need to buy a special tool from snap on for $80 that you would probably use once or good if you wanna help another member. Wish I took it to him earlier.