Exhaust questions

[SwampDonkeyXJ]

So I am pretty much dead set on getting the APN exhaust manifold and then having all of the piping, cat, and muffler redone on the 99 XJ. I had originally intended on running a 2.5" Magnaflow spun cat, and a 2.5" Magnaflow muffler but through reading install threads on here, I have come to realize that the outlet of the APN is 2.25". being the smart guy that I am :dunce: it seems to me that it would be pointless to make everything after the manifold 2.5" if it is going to bottleneck everything to 2.25" right from the start. Am I mistaken? Is there any benefit to running the rest of the system at 2.5"

Another question I have is which cat should I be looking to buy?

There are a few options that I have found:

Spun Cat (small but expensive)

Universal (nice and cheap) :thumbup:

Direct Fit w/ bung for o2 sensor (specific for XJ and has o2 bung)

Is there really any reason why I should pick one over the others other than price? I can't imagine that any of them would really perform any differently than another.

Thank you for any info you can toss my way.

 

[poorboy_616]

Borla makes a nice setup from the cat back, they also (IIRC) make a header for the late model 4.0L XJ's.

Sample of the noise. This is an 87 Renix 4.0 but you get the picture. Nevermind the door panel, if I set the phone down, it was gonna get run over.....