A few days ago I sent Flowmasters support a link to this video
57 chevy with flowmasters, and asked them what he thought this system was. Today I checked my email and this is the response I received from Flowmaster. Mike D'Addario Regional Sales Manager Flowmaster, Inc. sent me this response. I listened to the Video and it is hard to say what he has. The General Rule of Thumb is this....If you have up to 160hp you would use 2.25", if you have up to 250hp you would use 2.50" and up to 300hp and up you would use 3.00 for a Dual Exhaust Set up. You would want to use an H Pipe to balance out the sound, I don't think the truck in the video has one because of the way it sounded when he let off the throttle. I would suggest the Super 40 series mufflers as it will take some of the bite out of it. If you want one step quieter go with the Delta Flow 40 series. We sell a complete universal pipe kit including the h pipe in both Aluminized and Stainless Steel.
If give me a few things to think about now. Hope this helps some one too.
