Yes there is a bundle of ground connectors that bolt on to the intake manifold where the 2 manifold pieces meet. On my 87 Turbo with a manual transmission there are 2 copper pieces that the wires go into like a clip that bolts onto the intake manifold. One time I forgot to tighten that bolt and it acted very squirrely, dying randomly, etc. About the automatic Wiring, I cannot say, since I've never had one. You may be able to find something online at cygusx1 or in the back of a Toyota dealer shop manual for your year.
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/