I'm not sure if this thread makes me want to buy a set or stay away.

For what it's worth...

Pros:
Sounds awesome.

Cons:
Constant CEL
Expensive

It's a pain in the *** to dial in right. I thought it'd be hook it up and good to go, and I was completely wrong. If you buy, you need to expect that you will have to fiddle with it for some time. You probably should have a tune, another $700-$1000 item for the car (Putting you at well over 2K for the cats and tune). It's just not worth it in my eyes. I'd much rather of gotten a tune and change the exhaust out.

It's not that the cats are poorly made or VelocityAP isn't amazing, because they are, and everyone who have seen the cats say they're built very well, it's that my car at the very least is a picky little thing and it just doesn't really care for the new cats. Too much trouble to have to clear a CEL every 40 miles.

All, I have been working with VelocityAP on my XF and following this thread.
I am happy to announce that my MIL light is off and stays off.
New Sport cats, resonators, sport mufflers, pulley and Tune, all listed in signature.
No need for the MIL eliminators that most forums mention, just VelocityAP tune.

Tom - Is your tune written to switch off the P0420 and P0430 codes?

Yes, we have worked with Tom & Tested the mapping which will prevent the P0420 & P0430 codes from occurring without deleted them from the code.

with MIL eliminators - multiple codes
without MIL eliminators - 0420, 0430 codes
with VelocityAP tune - no MIL light

from my understanding... no not switched off, but code is written so the ECM never checks.
Mileage has increased modestly.
I am HAPPY, Smoking fast car, and Sounds FANTASTIC

I'm still getting these P0420 P0430 Post Catalyst codes and I'm starting to get used to clearing the codes everytime they pop up. I hope there isn't any limp mode the ECU goes into when the CEL lights up.

Still very interested in the handheld programmer from VelocityAP.

If it was going into limp mode you would know, it would rev over around 2500RPM. We can switch these codes off with a tune, but P420 & 430 won't result in any reduced performance.

I too am still getting my Christmas tree of codes. P129A and P129 B seem to come up the most, on long rides P0420 and P0430 come up too. P2098 and P2096 also appear.

It's not an install issue. I don't have any tune so it's competely confused. I've been to three different shops and the fits perfect. I'm kind of at my wits end other than doing a big expensive tune to see if it goes away.

500 miles on the car since the Velocity Tune. I drove the car after getting sport cats for a year with the MIL on. NO MIL. I am VERY happy!!!!
Thanks Stuart and the VelocityAP Team!

Stuart, I'll email you in a few weeks when I am ready to buy the handheld programmer. Thank you so much!

Finally got my pulley back on the car with the new supercharger and she feels stronger than she ever has. Just a few more miles to readapt the ecu and I should be good. The cats really made a difference in power. There is more immediacy in throttle response and top end!

Johncy,

Did you get the CEL resolved?

Not yet. In the coming weeks I will be ordering the programmer from Stuart.

Im getting a weird hesitation at 5000rpm at full load. The car feels like it falls off in power right at 5k and above and also hard time revving up. Does anyone know what could be wrong?

Hi Everyone,

Have a set of these back in stock for anyone who is interested

Moving to California and can't have these on the car anymore, selling my pair here: https://www.jaguarforums.com/forum/p...351-xj-170128/

Out of curiousity - sorry to revive an old thread - does anyone have these installed as of after 2016? This thread documents the journey through issue resolution but based on the welds I see on the cats, I am not sure of build quality, gasket fitment (old was a donut gasket, new is a flat seal on the flange) and the history here is a little confusing.

XJ doesn't use a gasket on the flange. The VAP cats will bolt up just fine for the earlier models but at some point, maybe 2013-2014, the slip joint at the end of the cats pipe was moved back towards the first center resonator. I'm sure it would be no problem though for a fabricator to cut the pipe and create a new slip joint.

Thanks! Upon second glance I looked at this photo without more detail, I thought they had a donut gasket style mate on the flanged end.

I am curious if anyone has installed recently, as of 2016 when this thread had its last post.

Hi Guys,

There's no ongoing issues with this product, although to be clear - it is not an emissions compliant product and does require ECU Tuning for cat efficiency.