How good was your repair on the cut? It doesn't take much of a leak to keep the vacuum motors from operating properly.
Perhaps during your repair or the installation, an upstream vacuum connection was pulled off?
As small as the lines are, I don't know that one could hear a leak, unless the end of the hose were right by the ear.
1989 F150 XLT standard-cab shortbed 4x4, 5.0L, AOD, 3.55 gears, manual hubs, 31x10.50 tires, 216K miles. Repainted Oct09.