I been kinda up in the air about getting me some exhaust for my F150 Limited 5.4L, I have Flowmasters on another truck of mine and I like the sound of them. I know for sure I want the turn downs(dumped) but not sure on the series as of now I'm leaning towards the 40 only because I think that the 50 series will sound almost like stock. Now I heard that the 40 series have a lot of drone(cab noise) which won't bother me as long it's not so loud in the cab I can't hear myself think. Let me know if any of ya'll are running a 40 or 50 series and how you like them.