Just to clarify that's a cylinder head not an exhaust header there is not a header in the world that will get you those gains. But yes you can expect to see big gains from the Hesco head only it's more like 20-25 hp on a 99+ 4.0 not 30. It's very expensive coming in close to $2000 depending on what options you go for but I think it's worth it. Not only do you get the power increase but you get a head that is 30lbs lighter than the cast iron stocker couter part. Not to mention the fact that you can even change the camshaft without removing the head. I just changed my cam by the way and it only took like 3 hours where as before it would've takin the better part of the weekend. If the price tag is too large there is another company out there making one that is nearly identical for around $1600. They are Patriot Performance and I don't know alot about them, but if you look around online you should be able to find them. I believe Summit was going to pick up those heads.......not sure though.
[B]1999 4.0 WJ Limited [/B] NX Wet EFI Kit;HESCO Head, Cam and Water Pump;Apexi SAFC2;Accel 24lb injectors;K&N FIPK; 2.5" Dynomax Ultraflow SS Exhaust; Dynatech Cat; Banks SS header;Custom 3" Head Pipe;E Cut-out;62mm TB & Spacer; MSD DIS-4; Jet 180°stat;H&R springs;Eibach Sway Bars;Brembo Rotors; Streetscene grill;E.L. Dash ; Autometer C2 EGT, N2O & Fuel Pressure;Edlebrock A:F Meter