Turbo Lance MP flux ?

I've been looking to buy a turbo lance and I've demo'd two of them so far.

One I flew was rock solid, but the second one the engine would not hold a
solid MP. It would flucuate +/- an inch or so especially on take off. We
even got the overboost light just off the end of the runway.

After seeing that, I am pretty concerned about the turbo system on the
lance.

has anyone else seen this problem? Was it just that plane or more of a turbo
problem that I would have with any lance?