Originally Posted by Mikester

To replace your under intake hoses on S13 SR, you need 3/4" hose (main heater line feeds, heater line to heater core & AAC valve air line), a section of 1" hose (one small junction to the top heater feed), and some 5/16" hose (throttle body coolant lines, AAC valve coolant lines).

If you plan to replace all those lines, it would behoove you to go ahead and delete the turbine coolant line between the motor & firewall. There is already a thread here on that very subject. Also, if you don't feel like cutting & fabbing heater lines, FRSport has an SR20 heater line adapter kit that plugs/plays with your existing tubing.