Just got this beauty, the boost gauge on idle goes to +/- negative 10psi.

When on the throttle, it does not go past 0 on the boost, the car has power but only like a N/A type car.

I actually drove this very car six months ago and it had all its power then.

Sometimes while in park the engine idles a bit higher 1100.

Transmission shifts a bit hard now and then.

Where to look???????

 

Start by buying and installing a real boost gauge, then get the codes.

 

I doubt it's the gauge, if it won't go positive at all and you're suffering power loss. It's either a massive air leak, or blown turbos.