the ebay full systems aren't bad i have the 3" turbo back catless it sounds good i left the silencer in the muffler just because i didnt want it too loud and get hassled all the time ..
turbo's love free flowing (intake,exhaust,charge) i personally dont like cats and have none on my car and if i do ever put one back on it will be a high flow cat.less restriction in any way means faster spool and more power