The MagnaFlow Street Series cat-back system (part 16638) is a stainless steel exhaust for the 1999-2005 NB-generation Mazda Miata with the 1.8L four-cylinder. It starts behind the factory catalytic converter, so the emissions-controlled front section stays in place while a 2.5-inch mandrel-bent pipe, a straight-through muffler, and a polished 4-inch angle-cut tip replace everything rearward. The manufacturer says 3D scanning during development produced a direct-fit design for NB Miata owners who want a bolt-on upgrade. Compared with a stock muffler, the payoff is a deeper exhaust note, a lighter rear section, and a build backed by a lifetime construction warranty. The manufacturer publishes no horsepower figure, so expect a sound and throttle-feel upgrade rather than a specific power number. Owners on user forums describe a tone that deepens as the muffler breaks in.
Shoppers searching for a 99-05 Miata NB1 or NB2 cat-back, a 16638 stainless exhaust, or a 2.5 inch mandrel-bent Miata catback will find the core specs below. Fitment is the main variable to plan around. Owners on user forums report that the new midpipe angle and inlet taper sometimes need adjustment before the pipe slides over the factory section, and one owner found the tip needed careful positioning to avoid rubbing the differential. Use the manufacturer's install sheet, confirm clearances before final tightening, and budget for gaskets separately, since the manufacturer lists them as not included. Installation is best suited to a home mechanic with a breaker bar, a cutting tool, and patience for the midpipe fit.
No. The manufacturer describes it as a cat-back layout that replaces the exhaust components from near the catalytic converter rearward, so the factory converter remains in the car.
The manufacturer lists gaskets or seals as not included. The kit does include clamps and the mounting hardware the manufacturer describes as necessary for a do-it-yourself installation.
Owners on user forums describe cutting the factory pipe at the point the instructions specify so the new midpipe can slide on. Some reported needing to adjust the angle or the fit, so follow the manufacturer's install sheet closely and confirm the cut location before committing.
The manufacturer designed this system for owner installation, and owners on user forums generally describe removing the old system as straightforward. The main challenge is the cut-and-fit at the midpipe, where the new section must line up with the factory pipe and catalytic converter outlet. Some owners reported that a rear brace bolt required a breaker bar to loosen. Plan on a breaker bar, a cutting tool suited to exhaust pipe, a jack and stands, and penny-style clamps or new gaskets if you want to seal the joints beyond the supplied hardware. Before final tightening, check that the tip is centered in the bumper cutout and that the tubing clears the differential and subframe. Owners have reported rattles when clearance is tight, so recheck after the first few drives.
