All the headers/exhaust manifolds have cracking issues on the 2.5 YJ & TJ as far as I have heard. My YJ just cracked its first manifold (in my ownership ~11months), so I have a pacesetter header coming in today ( i ordered the TJ model for my YJ for the different downpipe). However, what I hear helps is adding a section of 'stainless steel mesh flex pipe' at the end of the downpipe so that when the engine twists or whatever the hell else is making your exhaust moves, it's not as rigid.
Side note, my YJ ONLY has an o2 sensor before the cat. I don;t know if TJ's have two o2's or not and if the mesh flexpipe would be a leak issue for a post cat sensor. I doubt it, and havent heard of it... but just throwing it out there.
I chose the pacesetter for cost and that in Phoenix, AZ it does not see much moisture, and this is not a DD rig. placement of your flexpipe on the banks might be different because I'm guessing it doesnt come with a downpipe.