iirc RedRobin covered a substantial milage with his tbe without reporting any associated CEL.
....That's right - Over 15k miles. And furthermore I was (and still am) in regular contact with Milltek during that period and it was
always their advice to get a remap with a TBE as bacillus and chungster say. Their TBE's are developed with the reputable established tuner remaps in mind. Milltek are
performance exhausts.
You'll experience improved throttle response and nice sounds but nothing more without a remap. Well, you might gain 3 or 4 bhp at best.