Maybe it is just me, but I find that there are very few NA 1.8 exhausts that measure 2.5” in diameter.  Actually, the only one I am aware of is from Enthuza, and their standard unit doesn’t fit exactly what I’d like.  I am currently running a Springfield Dyno exhaust, and it is LOUD.  The Springfield exhaust uses a single Magnaflow muffler (located just after where the cat would normally be), 2.25” tubing, and a straight-pipe design which ends under the trunk on the driver side.  I’d like to try something a bit fatter and quieter, but retain the straight pipe design.  I’m thinking 2.5” pipes and two straight-through mufflers would do the trick, but it would have to be custom.  I spoke to Jeremy at Enthuza today.  He asked me to take some pictures of my car, mostly to measure the space available from the back of the rear subframe to the stock bumper. 

PICTURES: Current exhaust system (Springfield Dyno) and measurements.