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Reinstalling a catalytic converter


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Hello everyone,

Obviously I'm new here and looking for advice. I just bought an 05 GTi. I did not do my homework. I found out it has no cat from the turbo back! I'm going to replace the "test"pipe soon with a used cat. There was also a tuner that came with the car. My questions:

1) What are the pitfalls I need to be aware of before I install the new (used)cat?

2) Will I need to install the O2 sensors? If I do, will I throw a code and will it need to be reprogrammed?

3) If I don't need to install the sensors, will the engine run properly without reprogramming? (Long term)


Thanks in advance!

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Do you have a replacement converter already? If not, I probably have one for you.


1) no real pitfalls, maybe rusty bolts down there and you'll probably want a fresh donut gasket and exhaust gasket for the connection to the shorty piece of the downpipe.

2) if you have a stock tune on there you'll likely want an O2 sensor

3) there's some debate I believe on running long term with no rear O2--that it provides some fueling input.


Good luck.

"Bullet-proof" your OEM TMIC! <<Buy your kit here>>


Not currently in stock :(

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You have no cat from the turboback. And you mention it came with a tune. If it was tuned properly, you have a stage 2 car (assuming the turbo is still stock.) Throwing the cat back on without a tune is not wise. You'll most definitely have some issues. You need a retune if you throw a cat on.


As BMB mentioned, you *can* run without the rear O2, if the tuning adjustments are made to take it out of the equation.


What are you trying to accomplish here by putting on a cat? Pass emissions? Be friendlier to the environment? Serious question... because if you throw on pipe with a stock cat, you're going to be much slower. You'll be stock again.


Welcome to the forums, congrats on the car. It's not a GTi, it's an LGT or 2.5GT or GT. GTi is VW. And start searching the site for information and read, read, read. Go to Google and type in your search phrase and add in "site:legacygt.com" without the "s to the end.

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