1996 Pontiac Grand Am torque converter problems

I have a 96 pontiac grand am with a 2.4L with torque converter problems.It stays engaged for only a few seconds at highway speeds making the engine surge between 2000-2300 rpms.I have already replaced the TCC apply solenoid and valve,TCC PWM solenoid and valve,then the valve body,the torque converter itself,and finally the computer.It seems as though the computer is the one commanding the rapid apply since the solenoids are grounded when the surge is felt.No codes stored in the computer!!