Soooo, ok I think I got lost somewhere. Is this a '91 4.0L reg. or a H.O.? And you said you are looking to add the intake off of a H.O. model to your reg eng or what? Maybe this will help a little.I have a '91 H.O. 4.0L sport with a manual and stock it was pretty peppy. I have a big bore TB with a spacer, rusty's tube with K&N large filter, highflow cat and 40 series flowmaster. Recently added accel plugs, 8mm wires and new cap and rotor as well as an accel coil. Now, with these mods I picked up maybe 15-20 HP, maybe. BUT, the midrange torque and throttle response vastly improved, so good trade for me. I was looking into a different intake recently and noted that if you add a later model intake, say 96' up that you will claim about 15 hp. That's at the flywheel prolly, so maybe 7-10 at the wheels depending on any other mods u have. It has more flow almost double in volume. These guys are dead on about the diff in the reg and H.O. models about the head and intake difference, maybe chysler had other things diff as well, don't quote me. But in '96 when they went to OBD II I think, they lost 15 hp or so because of the sensors and the cats and u know environmental crap. HAHA But this website I was looking at places one on a pre-96 without these issues and there u go....easy 15 HP. Umm on the squeezin 50 more horse from this deal....don't lose any sleep ain't gonna happen....unless can u say, supercharger, or stroker? lol You may actually see 40 or so on the computer after installing ALL these things like I have in conjunction with the new head, but as far as real world, to the wheels power, expect a more reasonable 18-25 depends on the condition of your eng and how it takes these. But do expect to be able to tell the difference in power throughout the range and a bit of a mpg bump possibly. Oh, a shot of nos works too if you just gotta have that exact 50-75 hp...haha Good Luck! Hope any of this helps.
