I ran mine with OS 1040 pipe. It is by far the best I have tried (exp with VR12, NovaRossi, and Mugen). It is also the most expensive. Temp wise, it really depends on where and when I ran it. It ranges around 200 240F.
Get the Skyline VR12 Plus and end your guessing! This pipe will give you performance throughout the entire power band. Then you can work on getting the car and yourself capable of handling all the power!