Overboost on long rolling hills.

This is random, not very re-producible. I replaced the vacuum can and all the soft vacuum lines on my 02 alh last spring. My old can was rotted out for the 2nd time. Just did the n75 output test on both of my 02 alh vehicles. My n75 seems to make a chirp sound the first couple of cycles and then does the normal thump. Is that chirping or squeak sound indicative of a problem?

That would indicate that it's not snapping shut. If it doesn't change position quickly enough it could cause overboost in your situation. It's the small adjustments at the rolling Hill tops that can cause such things.

Swap them if you can and see if it persists, and/or follows the valve.

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