Throttle Body ?
 

Is the size different between 1998-2001 Throttle body ?

97+ should b the same if im not mistaken

Should be the exact same. Bore is 60mm but thins out to 55mm at the bottom.

Yea well i wasnt sure if they made them a bigger opening or not ..

No, you can get a 62mm bored throttle body for about $90 after the core charge. Everybody seems to like the throttle response and couple of ponys gained after the swap. I'm considering getting one when I get a few extra bucks.

Thats what i wanted to do with my'n too... Anything else You suggest i can do other than swaping out to a Bigger Throttle Body. what not to expensive?

I have a..

Throttle body Spacer

Cold Air intake

The throttle body spacer does absolutely nothing. That "increased throttle response" is a figment of your imagination do to your foot being on the floor. The CAI may help a little, but doesn't do too much, just sounds cool. The bored out throttle body is about all you can do to get a little more umph. If you really don't want to spend any money, you can just use a dremel and sand off the 55mm lip at the bottom to make it a 60mm straight through. Just mark a line at the throttle plate with a sharpie. After you disassemble it, make sure you don't go anywhere near that line or it will idle like crap because it won't have a tight seal.

Here's some good info on the process along with some pictures http://www.jeep-xj.info/HowtoTBboring.htm .

Myself i really appreciate this link because this has been of some interest to me for some time. I recently purchased a throttlebody from the JY just for this purpose and plan to do this soon as time allows. I will post up pics as i do the bore.

I'm doing the same thing, I'll probably get it for $10 with all the sensors included so it's worth a shot. I LOST a lot of power when I put on my Thrush Turbo muffler considering my cat is a little hollow due to previous owner and I haven't found time to put the new one on yet because it requires cutting and welding. My exhaust it too free-flowing and I have no backpressure, so I'm hoping it does a little something for me. Then I'm gonna wrap my CAI in a heatshield tape so it's actually cold and not warm. Last step will be 99+ intake manifold.