On one I run open carbs on the other a 20cm piece of rubber pipe.

they were like that when I bought them and I can't say much about the effect, except it sent us home from a trackday because of the wonderfull sound.

Cretins!
_________________
Poul
"If Life Gets Boring, Risk It!"
MC21SE, KISS box
MC21SP, HRC box, racing loom