db Killers and rpm flatspot

[cptmatt]

While I am waiting to solve a non-starting bike problem, I have a few other questions;

How do I remove db killers from my Termignoni's?  Is there an existing thread on this?

Also I seem to have a flat spot at around 4,000-4,500 rpms.  That is, the Duc accelerates smoothly and quickly, until it gets to 4k or so, then it kind of flattens until I punch through to 4,500 (and then it just rips right through to 7,500 real nicely.