I need more power in my car. I have a 98 2 door XJ with a 3 inch lift and 31x10.5 inch tires. It has the 2.5 litre 4 cylinder, which is no powerhouse engine. What would you recomend for me to add to my engine to get more out of it? Also, I am looking for a posi for my rear axle(chrysler 8.25") any suggestions? Thanks.

You have added 31X10.50 tires to a 4cyl car. Not a lot of go power to begin with. The larger then stock diameter tires (larger rolling circumfrence) have effectivly givin you a higher final drive ratio. Now your final drive ratio is not in balance with your power band and torque curve. Before doing any engine mods and trying to get more power have the ring & pinion gears in your front and rear differential's changed to a lower gear ratio to make up for the higher ratio change that you did when you added the larger diamiter tires.

Adding those tires was like hitching a trailer to your car.

Any driveline shop will know what ratio you will need to put you back in speck with the larger tires and they can do the install. You can also find ring and pinion sets on many Jeep accessory sites with conversion charts to get the proper ratio.

Without the proper final drive ratio adding more power to the 4cyl will just burn more gas, be harder on the drivetrain and give you only a minor differance.

With the proper final drive ratio your Jeep will drive like it used to and any power mods will really be noticeable and benificial.

Get a 4.0L