The tunnel plate was initially designed as a heat barrier between the exhaust and the torque tube, but the GM engineers discovered that a thicker plate reduced the torsional flex in the chassis, which was then used in the C5R race cars. With the tunnel plate already removed for servicing the drivetrain, this was a nice opportunity to upgrade the tunnel plate in my C5Z. The Elite Engineering and TPS Motorsport tunnel plates became all too expensive when adding overseas shipment, so I sourced a used C6 tunnel plate. Except for the increased thickness, the C5 and C6 plates are geometrically indentical, so upgrading to the C6 tunnel plate is plug & play. The C5 tunnel plate is an 1.6 mm sheet metal plate.With the introduction of the C6, the tunnel plate thickness was increased from 1.6 to 3.2 mm. The torsional rigidity of aluminum increases with increasing thickness. This is because thicker materials have a larger cross-sectional area, which results in a greater resistance to torsion.