blown97ss

iTrader: (8)

just want to see if anyone has swapped cats from a 02 camaro to a 99. i recently installed some 01-02 headers on my 99 ss and modified the stock cats to fit. i noticed that the 99 cat pipping is real small from the inside like 2 pipes are in the 2.25 inch pipe. i wanted to get stock cats from a 02 because of this and so i can bolt up my slp y pipe to it.

94Z28-MSTGKLR

iTrader: (20)

I don't know what your underlining goal for your car is but your really throwing money away. If you want to upgrade your exhaust put headers, ory, or catback on it. Swapping from 99 model year cats to 02 model year cats will net 0 gains in the real world, waste your money, and **** you off in the long run when you end up having to upgrade your exhaust like everyone on this sites will HIGHLY suggest you do if that's your intended purpose...

blown97ss

iTrader: (8)

just looking for small gains since i want this car to pass smog. i already have shorty headers and the slp y pipe also running a magnaflow exhaust.

trans_am7935

iTrader: (15)

unless you are in California, than you should not have an issue with Long tube headers, catted y-pipe and all emissions equipment. even some places in Cali wont care if you have the longtubes, but others will. as long as you get the cats right after the headers, then it should pass the sniffer.

94Z28-MSTGKLR

iTrader: (20)

You are just wasting your money doing a cat swap using factory cats. Does your inspection criteria require a visual inspection? if not, get a set of long tubes and a catted y pipe with a quality set of cats. There are thousands of guys passing smog like that. If your state requires a visual inspection then I don't know what to tell you. And shorty headers are pretty useless. Factory manifolds practically flow as well. And the SLP y pipe you have is a joke as well. These cars need long tubes and high flow cats, or an ORY if you so choose. Like I said, I don't know your exact requrements but there are guys on here that run long tubes, catted y pipes, any catback you can think of along with a nice set of ported heads and a pretty nice bump stick and are passing smog inspections.

blown97ss

iTrader: (8)

yeah im in california its a good thing i paid about 100 bucks for everything that i got. i know longtubes give alot more power i just dont want to worry about driving the car and running into a random smog check point and get screwed.

Zlow28

iTrader: (11)

whats the difference between a stock 99 exhaust and a stock 02 exhaust?

trans_am7935

iTrader: (15)

well i know the passenger cat is in a different position closer to the header, other then that, i think they are close to the same. pipes may be a little bigger.

blown97ss

iTrader: (8)

the 02 pipes dont have the extra piping on the inside like the 99 does. so i figured it would flow better.

dailydriver

Yes, all of those on here who will NEVER have to worry about visuals, nor roadside spot checks just DO NOT know how good they have it!!

blown97ss

iTrader: (8)

got everything put on it sounds better, it pulls more when u give it gas. going to the track to see if it actually made a difference or its just in my head. my best pass in the 1/8 so far has been a 8.5 @ 83.8 mph on the stock tune. hopefully i can get a low 8 after a tune.

94Z28-MSTGKLR

iTrader: (20)

Hands down, no doubt about it, that your tune did more for your car than swapping cats. If you swapped 99 cats for 02 cats, its 100% in you're head if you think you got any benefit from it.

roninsonic

iTrader: (3)

aftermarket high-flows would be your best bet. Vibrant makes some with a 4" core.

lemons12

iTrader: (71)

02 manifold does flow better than previous years.. Minimal, but better nonetheless.

dailydriver

These would NOT pass a strict visual in the Republik of California, nor other states with similar Gestapo-like inspection programs.

roninsonic

iTrader: (3)

Wouldn't know... I don't have emissions, inspection, vehicle tax, or plate fees

JDEP162

God bless ohio. So long as my plates are current, i can run anything i want with no worries or checks. As long as ur not waking the whole town at 3am with noise, nobody cares. Heard about vehicle inspections, but been driving 17 years, and never seen 1 , ever.

justin hover

Why would high flow cats not pass? Their cats either way.

dailydriver

Because they are not in the stock location (with headers) and therefore not close enough to the exhaust ports for quick enough 'light-off', and even if one kept the stock manifolds and welded the high flow bullets into the down pipe (in place of the OEM style catcons), they would not convert enough of the exhaust gasses to meet the Cali/50 state ECM's threshold (as measured at the rear O2), with out a tune which writes out the 420/430 codes.

Then they just WILL NOT pass a visual in the 'commie' (as so many on here would label them) states.

blown97ss

iTrader: (8)

i got some updates with the shorty headers 02 cats and slp y pipe i gained 1mph in the 1/8 i now trap 85 best pass so far was a 8.40. it might now be much but im not planning to go crazy with this car with mods just a fun daily driver. now im going to add a ls6 manifold and get it tuned looking to get a low 8. if that doesnt get me there some 4.10 gears will help. still have the stock 3.42s car is a m6.