There's a monster in my hatch!

[gs1000kat]

Or so it sounds. If I let the car sit for about 20-30 minutes and then restart it, there is a roaring kind of sound for a few seconds. It kind of sounds like maybe the fuel pump purging or something like a blast of air or liquid into a liquid. but I'm not sure. I've never heard it before on any previous 3S or any other car I've owned.

The car is a 91 with a 93 engine, harness and ECU. Only mods are Greddy Profec B, vacuum reduction and K&M air filter.

Anyone ever experience this?

*EDIT* So I havent found the issue yet, but a better description of the noise is that of worn brake pads grinding on the rotor. Not quite as loud, but a similar sound. It's obviously not that since I am not driving at the time. I also dont believe the sound is anything grinding, just the sound is similar.