In looking at a "standard" fuel delivery chart, it appears that mixture is leaned out at 4,000 RPM, then richens again at higher RPMs.   There have been reports of a flat spot in that range. Ratchethack feels the difference is not enough to account for the flat spot, and that there are other factors. motoguzznix also made comments to that effect.   Let's see if the collective wisdom of our members can enlighten us all, and give us a method of eliminating it.   Perhaps dlaing can insert t