the stutter is due to old pre-cat O2 sensors, i am pretty sure - i get a random CEL from it, usually after the stuttering happens under any kind of load.
unplugging the DISA definitely didn't remove that for me, but it did remove the 4k dip - and a bunch of low-end torque. 
i've got 2 new pre-cat O2 sensors waiting to go in. i have the conforti/shark tune. will reset the faults in the DME after install and will see what happens.
peter
peter
2004 330i ZHP
2005 330iT ZHP
2010 328iT M Sport
2012 128i M Sport