At very low RPM there is a puttering/burble sound in the AWE, especially when it's installed too low. The exhaust hanger needs to be preloaded; see the modifications
articles section for Gatorbites section as he explains how to do this and also Adax has an article that addresses this.
Exhaust leaks are typically a loud metallic clicking sound when the metal is cold, especially apparent around 2,500-3000 rpm in the AWE exhaust. When the leak opens up it will be present even after the exhaust heats up.
You can check what version you have by looking at the cans and seeing if there are two welded bracing rods in each exhaust or probably by calling AWE and giving them the serial number.