Depends on how bad.

The turbo has the capability of sending the boost well up over 25 psi. Damage to the head gasket is nearly a certainty at these levels.

The boost gauge that Lance mentioned is admirable, however, will you be watching it 24/7? It would only take a few seconds at 25 psi to do some damage, IMHO.

I run the '86 without an ALDA or a boost gauge and understand the risk that I've assumed. I rarely run the engine at maximum boost so I'm not all that concerned about it.