Retrofitted a Mazdaspeed3 Muffler on Naturally Aspirated NA
 

I've had a spare 1st gen Mazdaspeed3 muffler sitting around for a long time now. I went ahead and retrofitted it to my naturally aspirated NA now that my current muffler is on the fritz. From front to back, this system is: 1994 Miata 1.8L, factory airbox, factory header, TsudoN1 midpipe w/ 18" resonator, Mazdaspeed3 muffler. The results are below:

Before warming it up, the muffler has the potential to wake small children at idle and a blip of the throttle within my 40' wide residential lot. In a typically suburban neighborhood with large lots, I wouldn't think twice about the extra noise while the exhaust warms up.

Once it warms up, the muffler has a nice soft rumble at idle (similar to the speed3). With a blip of the throttle, and at low speed acceleration, it's a bit louder than I appreciate, kind of like a Borla or similar, but it does not drone or rasp which is pleasing.

Where this muffler really shines is medium to hard acceleration. It really loves the high flow and screams/rumbles at WOT. My plan is to take this out to an autocross with a decibel meter and see if it is within acceptable sound limits. It's hard to tell how loud it is to observers.

Pics attached. Video attached (more road noise than I expected, so refer to the time stamps below)
0:50 Idle to moderate acceleration into residential traffic
3:00 Moderate acceleration from stop light
3:50 Accelerating onto highway
4:17 Downshift and accelerate to pass
7:13 U-turn and accelerate back onto highway

Nice. What size inlet/outlet is the mazdaspeed muffler? How much space do you free up under the car? Enough to mount the spare tire down there?

FYI - Vibrant sells an almost duplicated muffler to the MS3, dimensionally at least.