I am thinking to buy up/down pipe for my stock EJ20, and I have HKS cat back already. Recently, I did some research about Perrin, HKS and Bosal, but I have no idea what is different those product and which one is best for EJ20?

Thank you

 

I've owned the helix and and stromung and liked them both. Personally I'd go with either the mad dad catted pipe or the ceramic coated stromung. Stay away from the hks, It's the same design as the stocker, sans cats. Check the reviews section, I think some were having problems with the wastegate sticking open with the bosal.

Do the uppipe at the same time.

 

id go with the helix

 

Yeah, good idea. I would recomend replacing the entire exhuast with a turbo-back (with or without a high-flow cat). Helix, TXS, APS are popular. Find a good deal with the sound you like and jump on it. If you are going to upgrade to a bigger turbo in the future, get 3" piping the whole way back for max performance. Keep the stock exhaust for future smog checks.

 

I'm no expert, but because of the difficulty in swapping an up-pipe back to stock in case of an inspection, it's probably best to just gut your stock up-pipe. The rest of the exhaust can be swapped back easily...but that up-pipe is a *****.

my 0.2 cents :-)

 

I've installed three different uppipes on my car and it is a *****. I went from stock to helix, helix back to stock, and now I have the bosal. If i were you I'd go with either the bosal or STi uppipe, both look almost stock and even have the stock heatshields. I'll post a pic of the bosal.