Sorry but in my personal opinion so-called "high flow" cats are a complete waste of $.

 

Pre Cat!? Never heard or seen such a thing. Just cut it out and save it for when you have to go back and do a smog test if your willing to take the risk

 

Later models have two "pre cats" in the manifold closer to the engine in addition to the main cat further down stream. The pre cats heat up faster and clean up emissions during warm up. Many new vehicles have multiple cats.

 

I bought a Magnaflow high flow cat last week, spent 2 hours trying to get the bolts off the existing cat to swap them out, no dice, couldn't even get one of the bolts to break free, the bolts/nuts are rusted together like nothing I have ever seen before and its above the skid plate, so i can't get to them to cut them off. Going to attempt again this weekend, if i can get them off and swap in the new Magnaflow, I will post back and let you know what differences I notice...

 

High flow cat on a 4.0 wrangler is not going to make any difference performance or mileage wise. There is just not enough in the 4.0. (on my heavly modified Mustang, high flow cats do make a difference). Total waste of $$ on the TJ.

 

The dealership I purchased mine at didn't believe me when I said it had 3 cats. I just got that smirk from the shop manager. Then after inspecting he agreed.

I don't know why people assume their customers are full of crap.