rough engine idle on 2000 Toyota Tundra

codes 300, 303, 306 . where do i start ?

Asked by for the 2000 Toyota Tundra
I bet you do have a rough running engine. You could have bad coils or plugs or both. You clearly have a problem with number 3 and 6 cylinder. To save a lot of agravation just replace all the coils and plus. They are double plat plugs.