I noticed this when driving back from Vancouver to Seattle this weekend. The engine pulls hard thru the entire rev range and does not make any strange noises when running. But say I am in 4th gear, at ~3000RPM, and floor it to pass, the engine sounds like it's knocking/pinging. But not really. Maybe timing chain slap? Engine has new e36 tensioner as of last summer. Otherwise, car runs great, idles fine. Only when I am trying to get power out of the engine when it is out of the power band. Ideas?