I know the JDM 4-1 has a 2.5 collector, but does the entire exhaust system stay 2.5? I wanted to put the jdm type R muffler on my car to quiet it down a bit but I have 2.5 bent all the way back from my JDM 4-1...so basically I am asking if the inlet on the JDM muffler is 2.5 inches or not...thanks