I keep hearing its the back pressure from the cats, and then I hear its the airpump. Well, today I took off my airpump, and I can tell they arent opening-it just dosent pull at higher RPM's like it did with it on. So does the airpump open them? I desperately need to know this, because Im having my exhaust fixed on Wednesday, and if the cats really dont matter, Im gonna take them off. But I thought if I did the ports wouldnt open. Somebody please hook me up.

 

IT's a mixed bag. They are opened by backpressure from the cat, but the pressure on the line is from the air pump. The back pressure is in the split air pipe which supplies fresh air to the cat. You can get the pressure you need from the exhaust with a RB header/presilencer combo.