I recently had a nasty metal scraping noise when my car was under load.. or near the stall point..(when taking off from a standstill slowly etc) Toyota blamed my aftermarket exhaust.. I removed it and the noise was still there.. *suprise suprise*
Anyway.. turns out it was the Drive belt tensioner..
I asked if it was a common problem and they said it had never happened before.. which is why it took so long to diagnose (2 days)