This isn't so much a myth, as it is exaggerated. The lines were put in by GM for cold climate conditions, which is said to cause ice to form on TB, which could cause a lot of problems, like a stuck open condition that can cause an accident. There have been no known reports of this happening, but there hasn't been any research either.


The idea behind removing it has nothing to do with the ice though, it is removed to keep the hotter coolant from heating up the TB. Cold air is good for a motor's performance, but the air moves so fast that the TB temp isn't really going to make a difference. Cooling the TB and Intake manifolds will help however.


The real gain from this mod is to eliminate one area that "can" leak, and if you tear the motor apart at all, those coolant lines can be a pain to remove when you want to remove the TB or the plenum. Because this is a really cheap modification, it is still recommeneded to remove the lines if you don't have to worry about ice forming on the intake (only because it would be bad to recommend something that could be potentially dangerous). Every little bit helps when cooling the intake, just don't think you will notice anything from it. Not only will you not notice anything, you won't get anything on a dyno because of it either (on its own).