installed one on my 97 4.0L – no difference, however, i got results from an aftermarket header and a freeflow muffler.

Actually the spacer is to increase the mass of the air charge and theoretically more mass will flow more into the chamber at higher rpm. Forget it. The small amount of increase is so small as to not exist. Do not waste your money.
Want to do something that works..???
Good luck

ya my cold air intake came with one and there is absolutely no difference between stock and after i put that thing in so dont waste your money on just the spacers they dont do anything.

A throttle body spacer is designed to increase the size of the mixing chamber on a throttle body fuel injection system, giving the air and fuel more time to mix. The Wrangler has a multi port injection system – the fuel is injected directly into the chamber – a spacer will have no effect at all. Total waste of $.

They were DESIGNED with carburetors and throttle body injection systems in mind to increase atomization in the air/fuel mix. The whole larger air charge thing is how they keep selling them to people with direct multi-port injection. All this is splitting hairs – it won’t do jack on your Jeep.

I installed one on my 97 TJ and never had any noticeable gains. I also put one on my 99 same results, couldn’t tell any difference there either.

A throttle body spacer will give you minimal improvements in gas mileage and engine performance (power). It won’t be noticeable if that is the only mod you are doing.