When you see aftermarket cams come out, the dip will look like it's gone because to get high end power it's going to sacrifice low end power, likely all before the dip making it look like a smooth increase instead of a spike/dip/spike.
I still stand by the stock header being the biggest contributing factor to the dip, there's too many dynos of good headers showing drastic improvements to not feel that way. From the nameless header thread, the 4-2-1 prototype with stock cams/heads:
