Yes it's 2.5" SSAC
The newer SSAC headers fit without any porting, especially since mine has larger primaries than say a 2.25". I fit the ve gasket on it and there is nothing to port. Some ssac will need porting.
car already have 5Zigen 2.36" (60mm) catback exhaust that came with it from Japan. The previous owner said it is 2.5" but my rough measurement told me its 60mm and the Japanese tend to use metric rather than inches. 2.5" downpipe going into a 2.36" exhaust shouldn't be a real issue tho.
My JWT pop charger is in Miami and should be with me in 1 week's time. However I wont install header, JWT filter and motor mounts until my clutch is here. Still hasn't left Fidanza factory, even after paying for it for over 2 weeks now!
Can anyone tell me performance clutches for sr20 are so scarce? It's a pain in the a$$ to get easy access to these parts. This is what the Honda fellows have over us - easier access to parts...