I've been doing some prototyping on a new exhaust system and replaced my own ERA sidepipes after wondering about restriction for years. After I did mine then four different buddies and customers through two different friend's shops replaced their sidepipes after hearing about my setup, and my friend Racyasp's SPF being the worst stock sidepipe muffler at a lousy 1-15/16" diameter core - Terrible! Then we tried a FFR, a custom JBL, and a few more SPFs and another ERA through my engine builder's shop - all showing noticeable results. The TWM injected SPF car picked up 40hp at the rear wheels. If you read other threads about sidepipes/mufflers here on ClubCobra, its turning out to be quite the "new find" among many of us 'round here.
A 392 stroker motor with the right AFR heads and sidepipe/muffler exhaust system seems like a great combination and affordable way to go.
