I have a Stihl MS270 with a rebuilt carb and a new Proline coil (OEM one went bad). It runs well now, and in the cut at WOT it's perfect. But if you're not under load, and squeeze the throttle, it will cut out and on and out and on every .5sec or so. I found it strange that it would be fine at WOT when cutting, so I slowly idled (fine), increased the revs (fine), increased revs even more (fine), then went WOT (not fine) where it immediately would cut in and out. Seems like a rev limiter issue. Coil? Any thoughts?