I doubt that your maxing out your injectors right now or after headers.
Theres an equation for seeing if your maxing out your injectors that i think Dr Jay knows, hopefully he'll chime in.
If your mechanically inclined enough to fab up your own headers, did you ever think about porting your throttlebody?
You might need some a/f adjustment after that, which could be done with a tech edge mini air fuel calibrator they sell them at www.zzperformance.com
With the 2.0 version, you can create your own fuel curve, which is good for dyno tuning.