Just out of interest - have you noticed a little restrictor inside the pipe between the T and manifold?
Its the shorter L shaped pipe...
Also the T\'d pipe on my car is called Hose 23 - not sure if that\'s original or I changed it - as I rebuilt it years ago and several vacuum lines broke during rebuild.
Standard 98 BH5 legacy with exhaust - 101k
BEB failure on piston number 3 possibly due to AFM failure some 6 months prior.
(this might be due to after market air filter attached? maybe the filter oil killed the AFM?)
Regular service however one on the 10k mark (it took a year to drive 10k)
Car hardly driven any long distance, lots of short cold driving. Hardly hit secondary boost.