1. nope, its just annoying to have the yellow light on the dash all the time.

2. You would need to talk specifics with the seller of the cat.

3. Similar. If i had enough money right now I would get the right cat for my accord and get on the dyno with the test pipe AND the cat to show the diff...but with one car broken down I have higher priorities.

4. I am partial to Carsound. They tend to be as good as other brands or better and are usually cheaper...I actually have an account with a distributor that sells Random cats though...