couple things to check if you think there's a hardware issue. I think you had another post about vacuum.
1. check vacuum lines from oil cap to after vacuum canisters. I do this by disconnecting at oil cap and WG solenoid in, apply about 15" from a vacuum pump and see if it bleeds off. Just cap the other side with you finger.
2. Now check post WG solenoid by disconnecting both solenoid outs, capping one (I use finger) and pump up to about 15" and check for bleed off (vacuum decreasing).
3. While on step 2 you can visually check WG movement. Top of the car for rear and bottom for front. Just make sure it's smooth. you can observe max vacuum to close rear and kinda judge this same movement length with the front.
4. Next start the car and check vacuum reading from pump... disconnect from vacuum canister and check. maybe around 25" hg
5. with car started you can check post solenoid. I do each separately and then together... if the reading from both are equal then probably good. You do need some WGDC to check this though. most are around 60% tuned as default.
7. check the exhaust flapper to see if any leaks by applying a vacuum
After everything above checks out, do a boost leak test. you mentioned you did this already. Sniz has a good DIY using a 2" pvc cap on the IC hot side. 20psi is sufficient.
hope this helps.