If you are going to weigh getting headers vs. not, these need to be considered. The cost of the headers and the replacement mid-pipe? Are the headers necessary to your goals (other words, what are your goals)? How patient a person are you (because they are really involved to install yourself)?
The cost aspect is pretty much up to you.
Depending on your existing mods you can expect around 10 to 15 rwhp on a stock to bolt on car, more on a blower car. Maybe you can find that power an easier way.
If you want to keep your sanity, the install will involve removing most the front
suspension, dropping the k member (a lot of people replace it with a lightweight tubular K member, yay more $$$$$), using a engine brace to hold the engine in place (got to buy an engine brace, yay more $$$), bolting the headers on (they will fight you the entire way), putting everything back together and hoping the headers clear the motor mounts, k member, steering shaft, etc. Then hopefully its all back together and happy, fire the engine to check for leaks (there will be leaks). Try to torque everything down until it seals (super pissed by the 3rd time it won't seal, takes many more attempts). Then once they are on, sealed, and happy in their new home, slowly drive it to the dyno because longtubes pretty much require a tune (yay more $$$). Don't chance the engine going lean, cuz long tubes do move that much more air.
Headers aren't just a weekend mod. They are a right of passage. You are a bolt-on Bruce Lee if you install your own headers in your driveway or garage, on your back, with no lift.
As negative as this all sounds, I'm not trying to turn you off of headers. Just be prepared its expensive, takes Shaolin amounts of patients and determination, there are mediocre power rewards. Also, the process is the same whether you do shorties, mid lengths, or long tubes. So if your going to do it and don't have to worry about emissions tests, go for the long tubes.
