Hey guys, a buddy of mine offered me a deal on his spoon n1 axleback + apex midpipe for my GSR. He said it would bolt right up so no fitment problems or anything like that. Now, along with that i was looking at getting a header. I've been noticing a lot of them have a 2.5in collector. I asked this guy about a header, because it said it was a direct bolt-on but 2.5in collector.
How could it be a direct bolt-on if the stock EM is 2in?

 

If it has a 2.5" collector, it will not bolt on without modifying or replacing the stock cat.