By adjusting you vacuum system, I'm going to assume that the vacuum control over the trunk lock was bypassed.
You say you can't open the trunk. Does that mean not even with the key? You should be able to insert the key into the trunk lock, turn it to the left about 30 degrees past horizontal, and push the button in with the key still in the lock.
With the button pushed in, then lift the trunk lid.
If you can get this far, then we can guide you through diagnosing problems with the vacuum control. It's so easy, even a girl can do it.
But if you can't get the trunk open with the key, then that's a job for a professional.