Hey all... I have this low metallic rattling sound at low rpm's, esp when the clutch is about to engage and it vibrates a bit... it sounds like a loose muffler, but a mechanic tells me it is the catalytic converter and it needs to be replaced totally, at about $450+. # 1, anyone else have this prob, and does that sound right? # 2, I found a cat converter for about $70 on ebay, does that sound right as well? I heard the install on these things suck, hours of work, welding, etc., so maybe $00+ does sound right on top of the $100 or so for the unit? Thanks!