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'10 WRB STi SE
115 Posts
Discussion Starter · #1 ·
Hey folks,

I have an auto 2000 RS that I am ready to replace the cat on. I wanted to post here and see if anyone had any other suggestions before I purchase the cat. The details are:

2000 RS (auto) runs top notch but only gets 19MPG babying it
No hesitations and issues at all.

P0420 came on, put o2 extender in, no more P0420! But only getting 19MPG driving like a grandma.

Work recently done:

Car has 150,000 miles.

New o2 front sensor at 131,000
Fluid flush, timing belt, plugs/wires, fuel filter, head gasket at 140,000

So my questions are:

Could it be the rear o2 sensor? Does it have enough influence over the fuel trim to get 19MPG?

Should I just go ahead and replace the cat since the o2 extender fixed the CEL? I found an oem-fit ebay cat for $199 (posted on thegolderfist build thread).


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