Upgrade Questions

I have a M6 99 Trans Am WS6. LS6 Heads, Cam, Intake, SLP Lid, Custom Tune, Pacesetter headers, Corsa Exhaust.

If I change my headers to stage 2.5 headers and a 224/224 cam, will I have to change anything else? Everything else is stock. What kind of HP Gain am I looking at, also any other suggestions would be great.

What are stage 2.5 headers? if you already have Pacesetter LTs, why change?
Oh yeah, where is the forced induction part of the question?

If you mean heads instead of headers, what is done to your current ls6 heads?