Installed Racing Mazda 4-2-1 system last weekend. Black jet-coated header after removing second EGR boss below top boss welded on for Proteges. Second boss is welded shut, but for appearance removed it. Header originally designed for Probe, but fits perfectly; J-pipe and mid-pipe bolted in perfectly--no leaks anywhere. Left the J-pipe chrome--can't see it. Midpipe is finished in black (dunno).
Installed second 02 sensor/spark plug extender fix in J-pipe bung and threw a CEL within 150 miles. Have an uninstalled resistor/cap MIL fix, but worked with a very sharp Mazda wrench and mucho $$$ OBD reader, and think we've come up with a simple, quick, virtually no-cost mod to extender that will definitely end all CEL problems. Installing today. More on this after I run a couple of tanks of gas or throw a CEL, whichever comes first.
Performance: quicker throttle response, smoother runup from idle , and definitely quicker from 3500-limit--acceleration is linear, no sags, no flattening out at the top. Dynoing shortly and will post results based on last previous dyno run--all mods are dynoed as they're added, so a true baseline is available for the latest.
Since both cats are gone, system is louder even though my Magnaflow CB contains a resonator. Since I'm not into "look at me" sound, I'm moving the resonator forward and adding a 22"x4" diameter Magnaflow muffler to quiet things down.
More after dyno and extender mod.
