Automatic Trans Malfunction

[BMR2NV]

ok guys i have a AUTOMATIC TRANSMISSION MALFUNCTION LIGHT popping its head up now and then! I own a e46 318i 2002 (im form australia) I have supercharged it with a custom setup! Now ive been having problems with the auto/step transmission! It will go into limp mode when at full throttle, driving at slow speeds i can just get away without the trans malfunction light popping up but it still happens now and then! Just before LIMP MODE LIGHT COMES ON the revs will just jump around like before actualy going into LIMP MODE. Ive taking it to a TRANS SPECIALIST they said nothing is wrong mechanically and it is some sort of ELECTRONIC PROBLEM? Now he recomended changing the TCM but it didnt work still got LIMP MODE? This problem is a pain in the ass can any one lead me in the right direction! Thanks