dr_bowtie

People dont like change....LOL

It makes sense to change them to high flow for that purpose or change the dual cat in a single pipe like on the I6-300... the double cat really restricts flow along with the HUGE factory muffler...

for putzing around town it is fine but for the extra power its something that can be changed... I still have 1 cat on my truck but no muffler and all the Emission stuff intact minus the rear cat...

why they thought they needed 2 cats in a row on the 300-6 is beyond me but you gain not only power, but also mileage going to a single cat...

Warlockk

Actually the reason they used 2 cats was the poor quality of cats in the early days, same reason they needed secondary air on a truck. They are actually 2 different types. The first is a 2 stage only effecting HC and CO. The second is a 3 stage that also cleans up NOx. The first lights off much faster to clean at cold start. In my opinion if your going to keep only one it should be the second. Or better yet switch to a better cat. The mufflers suck however as they are only designed to quiet the engine. They do that well though. BTW many new "clean " cars still use 2 or more cats. The adjustable cam timing is replacing that and egr however.

Just call me Sean

iTrader: (1)

Of course people are going to recommend keeping everything intact, but plenty of us haven't. My cat is empty because it was clogged, my air injection is gone because the pipes in the head were rotted out. I feed my children with that money. Just like I don't buy tires usually, I use what I find. There was a point I was dumping used oil in the truck because I couldn't afford to buy any.