Hello,
not so long ago i experienced how the t5 sounds raw when connection between cat and back muffler broke on my t5, i absolutely loved the sound but it was annoying as hell at the time since the buzz came straight from the cat to my ears and i had to get that fixed. Now mid summer i got custom made magnaflow like muffler which is basiclly straight thru. If i figured out correctly 850 t-5 don't even have resonators on them? My only concern is how to pipe the car to install the new muffler. I want to keep the cat and was thinking about piping it all the way to the end where there is muffler at the end. What kind and size of pipe should be connecting cat and muffler? How loud can i expect it to be?
Thanks in advance for all the tips!

edit; Should i expect any kind of drone while driving on highway?

 

you can buy (or build) downpipes, larger cats and cat-back systems. I believe the standard T5 piping is 2.5 inch and the upgrade is to go to 3 inch. Just know that changes to the parts may throw check engine lights which most tuners cure with a CELBOSS device to move the O2 sensors out of the direct airflow.