I ran two stock type PVC with two breather caps on my old Pump Gas Duster motor that had a small solid roller cam in it, 260 degrees at .050 intake side, 266 on the exhaust side ground on a 108 LSA installed at 1 to 2 degrees ICL installed with a stock type low deck six pack set up. Adding the second PVC made it idle a lot better(more air into the intake) and not surge at or under 1000 RPM up
That combination flat rocked, 10.25 ET at 127.+ MPH corked up with the air cleaner on weighing 3450 Lbs. with driver on Oregon 91 octane pump swill boogie devil

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)