My 99 cherokee sport has 86k miles.Auto Trans.
What's happening is the jeep has a noticable hesitation when accelerating on the highway. The harder you accelerate - the more pronounced the hesitation. Also with the Air Conditioning on, the hesitation is really pronounced upon accelerating.
Other wisse the jeep runs fine..
I have noticed a drop in MPG and HP.. It takes more peddle travel to get the thing to down shift to pass someone or going uphill.

Thanks !!

Have you had a tune up done on the car recently? Oil change, spark plugs, air filter etc...

If you haven't then thats what I would do first. Your spark plugs minght be a little toasty and warn if it's never been done.

Plugs was my first thought also.

I did a tune up back in April of this year. The Jeep has 86k miles in her and I still have never changed the plug wires. They are still stock wires. Could wires be the cause?
What would be the best plug to use on an XJ? Someone told me to never use platnium because they get too hot.

Plain old Champions are what people are using, based on other threads here; there have been problems with multi prongs, other brands, and other "special" plugs.

Wires could be causing the issue, and replacing them after almost 7 years isn't a bad idea.

When you did your tune up, did you replace the cap and rotor?

gas filter may need changeing.just a another thing to ck.

Gas filter on the 99 is part of the fuel pump inside of the tank and requires draining and droping of the tank.
Do the cap and rotor (and the wires if you got the money). Put some Chevron Techron in the tank ($8) to do a cheap clean on the injectors.

Thanks Guys.. I'll let you all know how it goes!