So my friend was driving my 2002 6-speed (without HLSD) on the highway when the car just felt like it went into neutral while it was still in gear. So when it's in gear and the gas pedal is pressed, the RPMs just rev with no power going to the wheels. Also, I can put the car into gear even without using the clutch, and the engine just revs freely.

I don't believe it is the clutch, pressure plate, or flywheel. I installed a Stage 2 Competition Clutch kit and Fidanza flywheel in April and haven't experienced any type of problem. I checked the slave cylinder and it's working fine. The shifter cables are also working as they should.

Anyone have any ideas?

 

You can check to see if the clutch fork is moving properly when the pedal is being pressed. If you remove the front part of the air intake you'll be able to see it on top of the transmission. The slave should push it about an inch or two towards the drivers side and (most important) it should come back when its released.