I was searching for HP - Torque charts for another thread on here and ran across a discussion about a turbocharged Jeep 2.5 liter. Interesting stuff to read about, but probably not all that practical or useful in the grand scheme of things. For a mere $5,500 or so you can have a TJ that puts down a whopping 170 HP and 200 Ft pounds torque to the rear wheels. That's only slightly more than the stock 4.0.
Despite Frank's woes with @Stinger, you're still better off with a Chevy V8 swap.
Despite Frank's woes with @Stinger, you're still better off with a Chevy V8 swap.