yes, or no to hollow out my cats on my T/A

**Her Names Dina** · 07-22-2007, 08:02 AM

I was thinking of hollowing out my cats. I've read that it fucks with the air flow and slows your car down. Others say it opens it up and unlocks horsepower. Has anyone dyno tested this and has a legit answer?

**daveb91** · 07-22-2007, 08:23 AM

I cant find the thread again but a couple minth ago someone dynoed before and after and got I think 13hp gain. Maybe someone can find it?

2000pontiac6 · 07-22-2007, 08:26 AM

Ive always heard it wasnt worth it. That there was maybe a 2hp gain. My O2 sensor got messed up just from adding a high flow cat so i'd imagine it would throw a code too

**Her Names Dina** · 07-22-2007, 09:00 AM

how much louder did it make your car and what brand was it. Also did you see an increase in power?

**Madcity T/A** · 07-23-2007, 10:10 AM

In regards to the O2 sensor If you get rid of the cats or put high flows on you should get a O2 simm.

**Mr. Luos** · 07-23-2007, 10:13 AM

Originally Posted by Madcity T/A

In regards to the O2 sensor If you get rid of the cats or put high flows on you should get a O2 simm.

I do not recommend sims. They don't always work out that well.
Some last forever, and others will throw a code after a month.

If you get hi-flow cats or hollow out the stockers....get the rear O2 codes deleted via a tuner. Shouldn't be any more $$ than the sims and it won't ever be an issue.

I have always heard hi-flow cats limit your power output by about 5 RWHP.
Knowing that the stockers are much more restrictive, I would think 10-11 RWHP for hollowing them out.