I read in another thread about some special programming that GM does to 1/2 lock the converter...supposes to save gas mileage. It causes a shudder while you're driving.

Anybody explain more about this special programming? My car has this strange shudder feeling when it shifts into 4th with very low throttle/RPM. It goes away after RPMs gradually or if I really push the throttle. It kinda feels like the converter is locking/unlocking/locking...etc...

I also hear this feature can be elimated by a tuner...will that cause other problems?