That kinda seems hard to believe though? When both my LS1's & my LT1 have been completely stock except for just the GMMG cat-back, the LS1 was louder at full throttle. Period. Does one extra cat really contribute that much more volume?

 

Look at the overall motors here. Being that a motor is a air pump of sorts, the LS1 pulls more air in stock so it is bound to push more air out. Not only can this be a part as well as 100 other things, take this into consideration. How many times have you heard a Borla on one car sound completely different from the same exhaust on another LT1 with the same mods? No two motors will sound the same. They may be similar but not exactly alike. This may be your missing link. It is entirely possible that when you go to long tubes the tone and loudness may not change at all, on the other hand it may make a drastic difference. The only way to know is go out on a limb and get a set and see how it turns out. I guess there is no real way to determine the tone/pitch/volume without getting really heavy into the science of all the bends and how the exhaust is resonating... blah blah blah.