I do know that PAC does make some of the Manley valve springs. I don't know which ones except that PAC does not make the Manley beehive valve spings.
I believe this to be not correct. I have used Manley and PSI springs in times past and am currently a very happy PAC user and WD. I am pretty sure but not definate that the Manley Nex-Tek springs are an Associated Spring Product. I used to think the top lines were pSI but after side by side comparing of similar rated springs I learned better.
About Valves, In Titanium I am buying Stealth now. Most of the guys are using either the Victory or Stealth now. Some are using Del West and the name of Manley seems to be slipping in quality. (My Sole OPINION). Ferrara seems to be the better in the stainless or the CV house brand. Rev is also ok.