These are details of the throttle body on an '01 ACR - Click on any image for a larger view. These are VERY large images for the best detail.   Inches mm TB Opening, Intake 2 7/16 61.9 TB Opening, Plenum side 2 7/32 56.7 Butterfly Diameter 2 1/64 51.2 Intake Plenum Diameter 2 1/16 52.4 Additionally, it appears that there might be enough aluminum to increase the diameter of the plenum about 3 mm, though that might be running a bit thin - about 1mm at the thinnest. However, it doesn't require the gasket of the old style, so I think it would be an OK setup. This gives you the potential of about 55.4mm at the intake side of the intake manifold.