Thx glen, figured so. I heard stock exhaust has valves as well even.
The stock exhaust does NOT have the same valves the NPP exhaust does.
NPP: Two sets of valves. One set on each of the outer pipes, just behind the mufflers, open under certain conditions to make the exhaust louder. The second, known as AFM valves, are further upstream and close partway when the engine is in 4 cylinder mode. These make the exhaust quieter
, not louder.
non-NPP exhaust: Has only the AFM valves. Even when they're open, the exhaust is quieter than the NPP exhaust when the NPP valves are open. It sound good, but is definitely not as loud or throaty as the NPP with the valves open.
NPP valves noted with Green arrow, below, AFM with red arrows. When the NPP valves open the exhaust gases bypass most of the muffler. With the non-NPP exhaust, all exhaust gasses pass through the full muffler path.