I hear a sound between 4500-5500rpms (where the max torque is of the turbo and the SR20 in general) that sounds like one of those cheap plastic annoying horns you blow at kid's birthday parties and on New Years. At first I thought I had a small hole in my boost gauge line since it sounded like it was coming from the harness firewall throughway area. Well I have my boost gauge disconnected right now and I still hear the sound. From the driver's seat it sounds like its coming somewhere like the passenger footwell, glove box, or the door jamb. Mike Jez said the AAC and/or IAC valve is over on that side of the engine bay and it could be leaking under boost. That sound plausible? Any other ideas anyone has? I can hear it lightly under any boost and is very loud under full boost between those rpms. I had my windows down once last night and I could hear the noise echo off the fences and houses around me. Ideas?