Are you sure it is actually pining? I had a pinging like sound at about 2200 to 3000 RPM's and it turned out to be the heat shield on the crossover pipe. Over time the shield will lossen up slightly and rattle under load. It may not be obvious by looking at it or even grabbing it. I took a screw driver put it on the top seem, and tapped it lightly till it moved back a quarter inch or so. Now it is quite as the day I bought her. I don't know if this is your problem but it's worth a shot to take a look.

Ryan