i am thinking to change my factory downpipe on my fd?
does it add any HP or no?

 

For you, Zero, you have those heavy *** mazdaspeed wheels

 

lmao. That's why you gotta sell them to Bwek .

 

You have a jdm car so you don't have the pre cat. I do not think you would notice any difference. If you decide to upgrade the entire exhaust you might gain 1hp

 

actually they are pretty light .... i know they look heavy but they arenot

 

I know lol im trolling you will you be at Kc Tmw night? If i get my cars throttle to unstick ill be there

 

yup

 

Unless the existing part is extremely restrictive, you would not be able to measure any difference.
I'm not sure which model you have, but on FD's, we have seen very high temperatures at the air filters (35-40 deg C) while running on the dyno, even with the hood open and fans running. This indicates that you could achieve some real gains (3-5%) by getting ambient air to the filters.
-Jo