Jeep

I have a 99 wj 4.0 ip and i really wanna get some more hp out of it know its no v8 4.7 but i know it can i dont know exsactly it does stoking my engine but i would like to know in the simpilest terms possible and if you could how much it would cost about$$$$ thanks in advance ps i get 14.1 mpg in city and 20 or 21 highway is 14.1 about right for a jeep ? thanks again also looking for an exshust for it thinking about a 40 or 50 series flowmaster comments also glasspacks ?? dynomax ?? turbo muffler all sound good to me tell me witch is better sounding on a i6 thanks again

It is a way of increasing the displacement of the engine by lenghening the the stroke (how far up and down the piston travels). on the 4.0 it is done by using the crank shaft out of a 4.2l engine. it us usually done in conjunction with a cylinder overbore and a few other mods. depending on how much you bore out the cylinder you usually get a 4.6 or 4.7 liter motor that puts out around 250 hp and 300 lb ft of torque. you can buy kits from different companies like hesco: http://jeepers.biz/. they usually run in the $1k range for a basic stroker kit to the $3000 range for pretty much a complete motor with tons of upgrades.two great web sites on jeep strokershttp://www.ajeepthing.com/stroker-motor.htmlhttp://www.angelfire.com/my/fan/stroker.htmlyour milage sounds about right to me, and as far as exhaust goes, i love the flowmaster 50, but its a matter personal pref. here is a link to sound clips of different mufflers.http://exhaustsoundclips.com/phpbb2/dload.php?action=category&cat_id=81