Think mine are on the way out. If you listen beneath the car and rev it a bit, there is a farty/nasty spluttering noise coming from them on return. It may be o2 sensor. are there 1 or 2 on each one?

 

if mine are shot, i'd rather replace them than bypass . Are they expensive new?

 

cheers

Mick

im sure cats are expensive, you can get sport cats these days, i decatted mine and it became extremely quick lol

think i've got as much power as i can handle now, without adding more, but i'll keep my options open lol.

I replaced my Cat's recently. As far as I know they were original OEM cats that had been on the car since it was build in 1990...Mine were stuffed, you could smell the sulphur smell and that seems to indicate stuffed cats. I checked out the price of new OEM cats. It was around $900 AUD each (maybe 300 pounds? not sure what the exchange rate is... all i know is buying parts from the US is cheap these days :) ) I didn't want to pay $1800 AUD for cats so I went for aftermarket MetalCats. Not sure if you have them over there but they're a highly rated metal core cat. Means that if you happen to hit a speed bump, the metal core isn't going to fracture like the stock cats would. it cost me about $600 AUD for the pair in 2.5inch Stainless Steel, they're high flow too so i thought it was worth spending the money on it.

you can see pics of my install thread here:http://www.aus300zx.com/forum/showthread.php?t=263917