I have a 2000 Honda Civic Si with turbo and 3 inch down pipe. The rest of my exhaust is stock besides the muffler on the end. I know that the turbo will keep the exhaust from sounding to loud. I have seen on many other forums that the Greddy EVO 2 has a deep tone and isnt loud and ricey (which i hope to avoid). I'm pretty fixed on getting the EVO 2 but my question being with my 3" down pipe what kind of cat or whatever should i need to get to keep the low deep sound? I want to allow my turbo to spool up quick but still have a full exhaust not some cut off. And also how big of diameter should i get the exhaust pipes keeping all the pretyped information in mind. Would like some feedback on whatever anyone has to say. THANKS!

 

Not saying you should do this but on my F-350 Diesel,I put a 4" down pipe and exhaust all the way out less the CAT, you are right ,the turbo keeps it pretty quiet,My next move will be to take the Muffler off. If you do this make sure you do a Cold air intake with as large a filter as you can use.

 

you need to keep it all the same diameter piping theres no point in having a 3 inch downpipe with the rest 4 inches. also you need a high-flo cat that doesn't restrict airflow. as for exhaust the best sounding muffler i have heard on a civic was an APEXI WS2.
http://www.youtube.com/watch?v=nlWhuy1lJ1E