[GuitarstarX7]

I wanted to do gears, but I don't want to lose gas mileage on the freeway. I was looking into installing either headers (long tube or shorty), or 1.8 roller rockers.
-Some companies claim 15-17 hp from 1.8 RR, but in reality its most likely 5-8hp tops.
-Some companies claim that headers will bring 15-17 hp, however, some say that the car will lose torque/power because backpressure is lost.

What mod would be better?

Current mods-
2004 3.9L/Auto
-Mac CAI/73mm Mass Air/Insulated(gets cold!)
-Dual Flowmaster 40s, H pipe (2.25 in pipe)
-42% Underdrive
-SCT Tuned

[Kyle F]

I would say go long tubes. IN essence you car will operate more efficently and if you keep your foot out of it gas milage should increase. Plus the sound difference will be very pleasing.

[lcurle]

Headers are a PITA to install, RR are quite easier, just watch the torque settings.

[Pinto]

unless you have some engine mods the headers won't help and could hurt you as far as HP and torque go