exhaust situation and question

[jpmxrider489]

right now i have a ported small 16g and ported o2 housing. i need a cat for emissions. my exhaust now has a stock downpipe, high flow cat, and 3 inch exhaust. where the exhaust connect to the cat is a 2.5 then opens to a 3. i have a ebay catback. i dont want to go buy a whole new exhaust. i would have to get a downpipe that can bolt up to a cat.

1 if my stock downpipe is 2.5 then would do better if i have a aftermarket 2.5. how would this make a difference.

2 since i have a test pipe that is 2.5 where can i buy a 2.5 downpipe that opens to a 3 then back to a 2.5

3 or should i just keep a stock downpipe.

i have other mods
16g ported
ported o2
afpr
evo fmic
190 fuel pump
catback exhaust
safc2

im new to all this as if my car is my first dsm. please dont flame i just want some basic awnsers. thanks for the replies

 

[wraoffroad]

the exaust flow is only going to be as good as the smallest point in the pipe since 2.5"l is stock you could save yourself a bundle by just using the stock downpipe. as for the cat u are gonna need it to pass emissions but idk if that ebay thing is gonna cut it. those ebay things are pretty cheap which causes me to suspect they have skimped on the valuable metals that makes them work. (i may be wrong ive never had one) also dont goto a test pipe without a rear o2 simulator.

 

[jpmxrider489]

so a aftermarket 2.5 downpipe wouldnt do anything?
would a aftermarket one make better flow

 

[Bud92gsx]

The stock piping on a 1g is 2.25.Are you sure the stock piping on the 2g's are 2.5? Don't go to a 3 inch then back to a 2.5, that's just going to restrict your exhuast flow..On a turbo vehicle you want the exhaust to be as free flowing as possibly..My suggestion would be to go 3 inch all the way back..

If the stock piping is 2.25 like the 1g is, then yes a 2.5 inch downpipe an exhaust would help you out..But why not just go with 3 inch so you wont have to upgrade later..

 

[Sik95TSI]

An aftermarket DP would help! Apexi N1 DP is 3" and replaces your stock DP and your cat! so you will be running straight pipe! Just keep your stock DP and Cat and put it back on there when it's time to smog or whatever that's what I'm going to do. - Ryann

 

[doubled07]

I'm from PA also. At what age is your car emissions exempt. Just something to check into. I know my 94 is exempt.