For headers:

3100/3400 Ported Exhaust Manifolds - Milzy Motorsports

Just added information about throttle bodies and "half shafting" a throttle body:
Mod Guide: Throttle Body Half Shafting - Monte Carlo Forum - Monte Carlo Enthusiast Forums

What kind of mods would you recommend to at least get my '04 LS up to 220 HP? I was thinking of doing a Wizaired CAI and dual exhaust with u-bend delete.

Besides the 220 HP mods, which ones, in general, will get me the greatest increase in performance/HP?

You question is best handled in a thread of itself. I believe the 3400 is ball park around 180HP if I recall. You are looking for a 40HP gain if I am right. My guess is that you are going to need more than these mods to reach that goal.

I have a pretty good amount of mods on my 03 LS and i feel like i'm maybe 180-190 at the wheels with them. My personal opinion is to just do simple stuff like a wizaired intake, exhaust, and a tune from Overkill. Save your money and maybe save up for a different car with power potential.

This summer i will be putting on my 2.5" down pipe from Milzy and seeing how much that does, if anything. Maybe one day i'll get on the dyno and see what i put down