im going to be swapping an L67 into my 97 se and i have pems and exhaust already and i want to get a down pipe. i heard that high flow cats clog up easy, so i was going to go with a catless dp. (no emmissions testin). what problems would this cause? i have heard conflicting reports. i have heard that no cat and an o2 simulator will effect performance, but my teacher for fuel systems said that the rear o2 only checks to see if the cat'* working properly. will the only problem be the code for no rear o2? if so, cant i get that deleted with a pcm? any info is greatly appreciated.

I"ve heard that it effects back pressure on your system. Your car needs proper exhaust pressure for fuel economy, ect. I busted all the screens out of my cat on my 93 Grand Am when I was in highschool because it was too noisy....BIG MISTAKE, my cars fuel mileage SUCKED after that and had poor accelleration till I replaced it with a high-flo universal cat. Not quite sure what it would do on your car, as I was too at one time an automotive school student (Universal Technical Institute). 11 months later, and 27,400 in student loan debt, the backseat of my Bonneville was my home for one week. LOL But you live, learn, and beware of what people lead ya into.

i know about back pressure, but i see all the gp guys putting on DPs. i didnt know if that effects out cars differently than a gp.

High flow cats don't clog any faster than a stock cat, but rather take LONGER to clog since they have more screen area to begin with.

Emissions testing or not, it'* federal law that you run a Cat everywhere in the US. Anyone that sees you without one can turn you in for a $250 reward from the EPA. Many shops also will not bring a car down from the lift if they see no cat when it goes up. My exhaust guy is one of these.

A high-flow Cat flows nearly as well as a straight pipe. Go that route.

Nooo...go catless and let me know when it'* done. I need the money.

Willwren is right about this, plus it makes your exhaust sound cool without hurting your wallet. Universal cats usually run around $60-90 at any part stores. I'm not sure if you can successfully override the O2 code with a mock-up sensor on an OBDII system. I know they make them for GP'*, and other W-body GM exhaust systems..., but it wouldn't hurt to try. I'd like to find out too if it works, that way I can replace my tired old cat without putting a strain on my wallet.

After looking for myself at some of the sites that offer parts of the L67 engine, mainly intense, zzp, and 3800 pro, ALL have Hi flo Cats or offer them on the site. 90% of the DPs offered for the GPs, since the B-ville lacks the space for a DP w/o modifying one to fit since the bodys are different exhaust routing between the W-body and H-body, you pretty much cannot get a DP that doesnt already have a Hi flo in it or welded to it. Not to sound mean, but anyone telling you that an exhaust without a cat is better for your car, is blowing smoke up your a$$

There is a simulator sold as well, I believe the PCM can have it deleted.

I still want the money...

Hi-flow cats flow very well, tame the rotten sound our exhaust CAN make in the wrong setups, and for the 50 or 60 bucks at www.justmagnaflow.com , it can save you big headaches down the road.

Some OBD2 Bonnevilles may still need an O2 spoof downstream with a high-flow cat.

but i livin in the middle of indiana. nobody cares about emmissions here. one of my friends almose got arrested for 105in a 55 in a riced out mazdaspeed protege and he had no cat.

dont jimmyp dp'* fit?