I have searched the forums however I have not seen this topic discussed. The guys at Pypes are telling me their Race muffler has less drone than their Street muffler because it is not chambered. What is your experience?

It makes sense, and if you look at the decibel charts, you'll see the same thing.

I have the Street Pro's, and I don't get any drone with them at all, particularly not like the flowmasters they replaced. They are kinda loud when I get on it, though, and the race mufflers will be louder when you're in the throttle.

All welded performance mufflers are going to have a certain amount of drone at certain rpm levels. Neither the Street Pro nor the Race Pro have excessive drone. If you run our X-pipe the drone will be even less.

Depends on the size you get
I had the StreetPro in the 14" or 16" cant remember the size, but in the 3" version, and it resonated real bad. Its a shame cause otherwose it sounded great.

Here's a clip w/3" StreetPros w/Xpipe:
http://s134.photobucket.com/player.swf?refURL=/&file=http://vid134.photobucket.com/albums/q116/VGIORDANO_2007/Chevellestreetpro.flv&fs=1&os=1&ap=1

I recently installed the complete 3" Pypes system with X crossover and their Race Pro mufflers purchased at CB '07.
Reasonably quiet at cruising speeds but comes alive at full throttle. ;)
I'm pleased with them.

I installed the "Sweet Thunder" brand, 3" chambered system (sold in 3 diameters) on my 69, with headers and an X pipe. The pipes themselves are the mufflers, with a chambered resonator out the back. No drone. Has a nice deep rumble at slower speeds,,,, rips open like a dragster when you hit it. Very pleased with this system. However, it IS loud at RPM.