[JL8Jeff]

There's a lot of science involved in exhaust systems so it can't be fully explained. But I've seen tests done on a 67 Firebird with a 455 and putting dual cats on only hurt the 1/4 mile time by .1 while the dual mufflers hurt by .27. A cat is not attempting to quite the noise so the exhaust flows straight through while the catalyst does its job. A muffler is basically an expansion chamber that allows the exhaust and noise to expand and that's what starts to hurt the flow as it's funneled back into the outlet pipe. I was at the Englisthown show one year and the guy next to me had dual cats on his 86 Camaro and no mufflers and it sounded great. He was running the Edelbrock EFI system on a built 383. He said he could feel the power loss with the mufflers on it so he removed them since the exhaust sound wasn't that loud with the dual cats alone. Removing the cat is only necessary if you plan to lean out the mixture so the engine is on the ragged edge of a meltdown. You'll make an extra 5 hp but you'll blow the motor in short time so why would you do it?