360 Exhaust Upgrade

I just bought my first Ferrari. I got it from an estate and have no history but did get a PPI. All checked out pretty good but since I have no history I am doing a major service, replce blown clutch and service INOP A/C system. While all is apart I am going to replace the exhaust. I just got a used set of Fabspeed headers with the blankets along with their older Muffler (see Ebay auction # 133667560873 ) for specifics. The system was missing the cats / bypass pipes and the exhaust tips. I am leaning toward the Cat bypass pipes and leaving the stock tips (w Valves). Not really sure how this will workout as I'm not quite sure if the muffler is designed to utilize the stock valved exhaust tips. In addition I have heard / read about O2 Extenders for the cat bypass pipes. These "extenders" appear to be just very mini Cats that I suppose trick the ECU into thinking the Cats are still in place. Is that true. Most info on the subject does not really get into it in detail. At first I was considering buying the complete current system direct from Fabspeed but I just could not wait the 8-12 weeks for delivery; but in that system Fabspeed has you send in the ECU's to be reflashed. My mechanic says that is not necessary. More conflicting info. Another item just for fun, Dan from NormalGuySupercar on Utube has convinced me to utilize the Muffler from Kline for both performance and sound, + add The Forza control so I can manually control the Valves. So in conclusion- Ultimately Fabspeed headers w/blankets, Capristo Cat Delete pipes, Kline Muffler and tips (with valves) will be my final system. Do I need to flash the ECU's and/or buy the O2 Extenders? Answers to any or all of these questions will be greatly appreciated and if I need the "exteders" where to buy them.