Installed my catless down pipe 2 days ago and the check engine light turned on. I've heard it's normal when running a catless dp without a turn. Now if I buy a Cobb accessport and use their ots tunes will it automatically turn off or do I need to get a custom tune for my car?
You will get a CEL with the Cobb OTS maps. To eliminate that occurrence, you'd have to get a Protune (custom map) from a Cobb Protuner.
Some people make O2 foulers as a solution. It involves combining a couple of spark plug non-foulers that you can pick up at Advance Auto or AutoZone for a few bucks. Try Googling 'O2 fouler' and you'll quickly see what I'm referring to.
The best solution would be to have it turned off in the tune, but if you want it gone before you purchase a custom tune, then there's other options available.