[RickyB]

ISC coolant lines will have no effect on an IAT (Intake Air Temperature) sensor which is by definition a sensor mounted on the intake pipe (pre-turbo).

ISC coolant lines will change the reading measured by a properly placed MAT (Mainfold Air Temperature) sensor since the purpose of the lines is to warm up the idle air reaching the manifold. The computer will do the right thing and the car can be set up by a competent tuner to run and idle like a swiss timepiece.

The purpose of warming up the idle air is that fuel atomizes better in warm air and thus the car will idle better with lower tailpipe emissions when the idle air is heated. It would be great if the idle air were heated in a location away from the thottle body where the coolant lines will also heat the thottle and the manifold and have a small effect on power when the motor is not at idle.

Removing the lines is a personal choice. I would not recommend it unless you live in an area where winter temperatures are very moderate or you plan to never drive the car when it gets cold. It's details like the ISC coolant lines that help a stock car idle so well. Just keep in mind that as you build the motor and place an emphasis primarily on making power that you will lose some of the nice qualities of the stock setup. It never fails to amaze me how many folks build a race car setup and then expect the tuner to be able to make the car idle like stock. My first rule of modifying cars is: if you want your car to behave stock, leave it stock.