hi there everyone, i have a question, my JDM TT still has its standard exhaust, to be honest prefer to keep car standard in a way, but took a look at the exhaust on my car the other day and well its looking OLD,very dark rust colour, not blowing mind, got to be same one from factory, wondering about the BPU thing and exhausts, as long as i keep the cats on the car will it matter what exhaust i put on cat back as am not looking to increase power at this time. will i have to use restrictor rings and other bits by just replacing cat back, sorry if it seems like a daft question but i want to be sure, new to the supra, owned an s14a for the last 4years.