Long term fuel trims for heads and cam question

[hpcubed]

Did some logging. My trims are all in the -9 to -15's in the lower half of the map values. I can understand my volumetric efficiency being less than a stock heads and cam at low rpms but it seems that by 4000 rpm, my engines VE should be better than stock? Is this typical for a heads/cam engine? I have long tube headers, how much does this effect the accuracy of the O2 sensors?

[hpcubed]

New discovery: My VE tables started as stock. I now notice why I am running rich. The backup VE table is set up much more conservatively than the main from the factory. (According to the stock tune reference I have).