[CSG Mike]

Originally Posted by tomm.brz

your in-house tuner keeps CL fuel control active it won t run leaner or richer, maybe just transiently because of the integral/proportional corrections, but anyway afr is going to be quite spot on all the time

only bad things I would think of about upgrading to catless without returning, is the performance left on the table
ecu won t rise ign timing more than it is allowed to, and cam timings could be made more aggressive and with less overlap at higher rpm
also at lower rpm and loads it could need some fix

We're referring to the factory tune. There is no "custom" to the factory tune.