Yes they sure do, and I saw 2 psi increase as well. The stock inlet you get from Vortech is trash as well as the discharge tube. I'm trying to custom make a 3" discharge tube for myself b/c no one sells them.
I have a guy that nakes them here local..I can have him copy mine..I'll ask see how much if your interested (but mine is for the Fox setup)
Then paint it to match the rest of the bad a s s paint job
He can powder coat it also if you want.
Lemme know I'll call him and get a price.
For mine i went to a local muffler/exhaust shop and had them bend a piece of 3" exhaust. I know its not chrome though, but if your interested the best way to go about is to take a piece of wire and bend the angle in it you need and take it in. They then will bend the pipe exactly to the way the wire is bent.
Cost me a whole 5 bucks.. And another 5 bucks to weld on a small tube for the BOV.
Oh and by the way. Vortech rates their s-trim as 6-8 psi i believe. According to my data log i made 12 psi under 6k rpms with my AFM power Pipe and custom dischage pipe.
Now were are the number that 12psi on a 331 should be making? Im not really sure? Im still looking.. lol