Hi guys, I'm trying to rectify an odd idle on my 2004 JDM GT-B. It'll drop down to 500RPM momentarily when I come off the gas, but only occasionally. My understanding is that this is a symptom a vacuum leak, but I'm wondering why it is intermittent, and frankly, it's driving me nuts. Could it be a sticky PCV valve? If so, where is the PCV? Any other ideas? I recently pressurized the intake with a bike pump and sprayed soapy water on all the joints in the intake without finding any leaks, and the issue is still present. Admittedly I haven't checked the exhaust-side joints for leaks but I can't hear anything there when the car is running. Seems to boost fine and am seeing 1.4 bar on the gauge. The wideband shows acceptable a/f ratios throughout the running range, although it goes lean when I come off the gas. The car has an HKS mushroom filter cold air intake pipe, and full HKS turboback exhaust (with a cat) and a tune but is otherwise stock. Plugs are fresh and it's not throwing any codes. I have a tactrix and wideband, so I'm reasonably well equipped to try diagnostic suggestions. Thanks in advance!