[Ronnie's.930]

I know you said you tried grounding the overboost sensor/switch, but were is it mounted? I ask, because the part it is mounted to needs to be well grounded. For example, when the switch is in the stock location, if you powdercoat the recirculation housing, like I did, then a wire has to be run from a bare spot on the housing to a good ground point (in order to ground the housing as it is now insulated by the powdercoat). If your overboost switch is now mounted in the intercooler, the intercooler might not be providing a good ground as it is isolated via the hoses . . .

Another possible problem is that one of the two fuel pumps might not be working at 100% and it shows up under sudden acceleration. You might start by flowtesting each one separately. I know there are some past threads detailing this process . . .