Overboost on cruise control...

[Doggy]

Yes, more or less.....

It's got a variable turbo & no waste gate. The turbo actuator is vacuum operated and needs vacuum to reduce the boost.

The problem will be down to either a vacuum leak, or something limiting the rate the vacuum can be applied to the turbo.
(Mine was a split diaphragm in the swirl actuator, GingerMagic's was a partially blocked vacuum restrictor in one of the vacuum pipe tee-pieces).

Only trick is finding it - since your's only does it climbing a hill, you have a minor leak / restriction.

[GingerMagic]

The restrictor is built into the 'T' piece that clips onto the vac pump, and also on the servo end.

Once you have simplified the vacuum system, you only need a 2 way outlet clip on the vac pump ( 1 to turbo EV, 1 to servo ) which will hopefully make things better.

Do you have access to a hand held vac pump? You can measure the vacuum before and after the EVs to eliminate them as suspects

[Doggy]

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[GingerMagic]

I believe if you are overboosting, the wastegate isn't opening fast enough, or not at all - the vacuum reduces the boost by opening the wastegate...

[Doggy]

One sure way to find out - disconnect / plug the vacuum supply pipe to the turbo/wastegate control valve and CAREFULLY test.
No boost = vacuum need to close wastegate.
Normal/overboost = vacuum needed to open wastegate.

[steve_earwig]

WHen the mechanics accidentally knocked the vacuum line off the turbo on mine it was a slug, so I guess it needs vacuum to close