I have had a ton of 350 cu.in Chevy Suburbans. I get all my maintenance done at a shop where they also build race vehicles. So they know ALL about Chevy engines. They always put on a single 3 inch pipe with a mid range muffler---by mid range I mean slightly louder 2 baffles as opposed to 3. This set up allows for exhaust to flow better--AND maintain the correct back pressure. I had it re -done least year on my 1999, 350 . So-- with all new hangers, clamps--custom bent 3 inch pipe--muffler--new O2 sensor and new catalytic convertor---it was 900 dollars. Thats from the motor back to the rear in the stock configuration. Most people put new mufflers on old pipes with old convertors and never replace the sensor---thats why you will NEVER see any performance upgrades. Save up and have it done front to back and all NEW stuff. There's more to it than just noise!!