Mechanic didn't torque the bolts properly $7000 in repairs

[Sergiu]

Newton Bros replaced the spacer plate, cap screws, o rings, gaskets, inspected the gears and installed everything back. But during a test drive the engine was making a grinding noise above 1300 rpm, and the gauge that measures intake manifold air pressure was climbing in increments not in a fluid natural manner as it was before. At this moment they don't know what's the reason of that noise. Any ideas ?