[jluetjen]

I'd start out by getting some 32 mm venturis -- 30's are most likely too small for your usage, especially since you do a lot of WOT on the track. They most likely give a good strong signal at low rev's (possibly contributing to your richness at lower revs). At the other end of the rev range, 30 mm venturi are most likely fine for an engine that peaks at 5000 RPM, but with your E cams your engine is most likely capable of generating peak HP up to around 5700 RPM. 32 mm Venturi should be about perfect. If it were me, I'd replace the venturis and the mains first, and then see how you're doing.