Originally Posted by Jaxster
I recently had my cracked exhaust manifold replaced with a header. Since the install I have witnessed an improvement in power output, say 5% maybe 10%.
The stock Tj from 2000-2006 with the I6 has 190hp, and the 1997-2002 I4 as the OP has, has 120hp . I respectivly dissagree that you could have gained 9.5 to 19 hp with an I6, or 6 to 12 hp with on I4 with just a header swap. Though it may improve some driving and response aspects of the jeep, it's not going to be a drastic change as you say.