It feels like a small bogging, right?, at the dyno it looks like spikes or a dirty line. In my case this happened when the advance curve goes in too fast, what we did initially was to set total timing to like 6k RPM or something like that. Currently what I did was to set idle timing higher (18) and pull in the advance to 3800 RPM and seems to work fine.
My engine currently has platinum plugs, which is not what hughes recommended, but my mechanic put them on, and I have had no time to replace them. I will change them to see if there is any difference.
