Stock exhaust manifold vs Gibson header

[Sflxj]

I have a chance to get a good deal on a stainless Gibson header for my 96 XJ. I'm currently running the Cat and a Flowmaster. I have 4 hole injectors and I'm planning on getting bored out throttle body and a less restrictive air filter. Is the header going to make much difference in performance?

 

[jbmoose]

Sure. Especially with all the mods u have listed. And while u have everything off, might wanna get intake manifold ported and polished. if it was stock, u might get 3 to 6 hp out of it. But with cat, exhaust, TB, bigger injectors, filter... Could possibly see 15+ hp out of it.

 

[jeeptech1]

na. had one on my 98 wrangler. i also had new cat, high flow muffler, k&n cold air. did not notice a bit of difference performance or gas mileage wise. only thing it did was make the motor shinny!