Our Sport Cat Downpipe is 100% the best route to go. It is a simple bolt-on and go have fun modification and being CEL free. I definitely do not recommend running a catless downpipe without a tune. There are a whole host of issues that could arise from that. Just because you didn't have issues in the past, doesn't mean the car was running healthy.
Check your PMs - I'd love to chat more about getting you set up!
Also our dyno results are from a direct comparison of the stock M2 then Sport Cat Downpipe installed. Both tested in the same day and under the same conditions and with awesome results!