Hi guys, I drive a 2001 WRX Bugeye.

When I drive it, if i apply any more than, say, quarter throttle, the revs will hang, or rev out when I let off, regardless if I engage the clutch or not. I've already done new clutch, new throttle body, new throttle cable and all new sensors.

I've been told could be VAC leak, but I just wanted to hear other peoples experience with this and how it was rectified in their cases.

 

Could be a number of things,there are a few recent threads on here about the same fault,could be faulty O2 sensor or NPS Did you fit a new TPS with the throttle body? could be a faulty TPS if you didn't?
I would try resetting the ECU see if the fault disappears,it's even worth buying a cheap vag cable so you can datalog and see the sensors values.

 

get some soapy water in a spray bottle, and spray around the hoses etc, see if there is any change in the tone/revs of the idle, this may help point towards a iffy hose.