Spartan 1771

You could go with the following:
1. Dewala air intake guide
2. Three inch intakes, but you'll need a retune
3. Port and polish your throttle bodies
4. Upgrade your throttle bodies with the Daytona throttle bodies, but you'll need a retune
5. Swap out your upper intake manifold to a Motordyne or Z1 model, or have yours ported and polished
6. Port and polish your lower intake manifold or upgrade to a Z1 model
7. Light weight / under drive pulley (I know there are mixed opinions on this, but it is an option)
8. Consider a better cat-back set up
9. Delete the HFCs and get test pipes (you'll increase rasp)
10. Upgrade the cams, but that's expensive and labor intensive.
11. Like you said, you can upgrade the headers, but your drone and rasp may increase. I can't speak to this because I haven't upgraded them........... yet.

I can't think of anything else right now, but if I come up with anything, I'll respond with it.

__________________
~Rob

-DD Air Guide, Stillen G3 CAIs, 63mm Throttle Bodies, Motordyne M370, Berk HFCs, FI TDX CBE (non-res, CF), Sprint booster v3, Ecutek Dyno Tuned, and the list goes on...