Don't waste your money on the spacer. Go with the 60MM TB instead. You will gain a little more power. Not a HUGE power increase. Just a little. I just did mine. I got it from a junkyard from a Cherokee with a straight 6 for $25. If you opt to do this just make sure that you get one with a MAP Sensor if your Jeep has one. The first one that I got was from an older Cherokee and it did NOT have the MAP Sensor. And second, when you install it make sure that you take notice of the tabs that are on the TB and intake manifold. If you put the TB on wrong, the tabs will touch and when you tighten it............CRACK!! And the TB is now trash. The one downside to this is that the opening in the intake manifold is smaller. So if you can, bore it out to match the TB. I didn't feel like taking the manifold off at the time so the air technically does bottle neck.
Here is a link from JP Mag about little things that you can do to get a little more power out of the 2.5 liter.