MarkT wrote:
"Baffles in a true "sleeper pipe" remain intact... they precisely added an internal cone inside the original exhaust to reflect pressure waves. This boosted power by making the stock pipe act more like an aftermarket two stroke expansion chamber."

Actually the baffle plates were removed on all Sleeper Pipes that Dave and I made (in my garage). A cone was then made and placed as far back in the pipe as possible that the original spark arrestor assembly would allow. We never removed the spark arrestor as we wanted to our Sleeper Pipes to always pass an inspection .

Most Sleeper Pipes were only slightly louder than stock although a few were a little louder .

Thanks DVM... baffle "plates" is not what came to my mind... please correct me if I'm wrong but those are more a "liner" that originally had a thin layer of mat underneath.

My definition of "baffles" are the spark arrestor and muffler inserts at the pipe outlet... the ones we removed and threw away as kids. DOH!

The original post may have meant the baffles as the "liner" as you described...

And it is subjective but I still stand by my statement that the great "sleeper pipes" you and Dave made sounded a bit "crisper"... not really "louder" to my ears.