Jsn, for giggles, pull the idle needle out and see if there is a scratch, flat spot or other defect in the needle itself. It may be bent, placed off center in the threaded piece, scratched or just a bad grinding job. Mine runs well and so do others so that makes me think it is a case of QA/QC in the idle needle or the spray bar. You might have to use a loupe to see the needle better.

Dru.