I'm driving a 2005 6MT REVUP - I started my car this morning and it was idiling around 2500RPM and this really loud unusal rattle was coming from the front of the car near the plenum. I started inspecting the car, undernath checking the splash guard, heat shield, bolts that may be loose but couldn't find anything.

I started driving the car, and in 1st and 2nd gear if I let off the gas and if I downshift and slow down regardless if I'm in gear or not the rattle noise comes back. No rattle in 3rd gear+.

I took it to a friends shop we couldn't notice anything - I am just looking for suggestions?

clutch? flywheel, bearing?

thanks