So I got the invidia n1 dual exhaust and now want to get an aftermarket y pipe but I can't find one that is 2.5" all the way through?? Their all 2.5" -> 3.0" outlet. was this system designed to use the factory y pipe or were they just not thinking about the fact that there's no 2.5" y pipe?

 

Thought Tanabe had a Y pipe that was close to what you want...
Youcanalways have one made.Did you check Motordyne?