OK, for early body cars see below. Some variation between CIS and Ljet and LH Jet euros. Note the voice-over for some points not shown on these diagrams.
Point 9 (9a and 9b) There are two crucial ground attachments on the 16V passenger side cam cover. They ground the engine electronics & the injector harness.
One is at the top of the "O" in the word Porsche cast into the cam cover --- and it may be covered-up by the emissions air injection valve/hose. The second attachment point on the cam cover is more visible and is closer to front of car.
Point 10 For later Euro cars, look for ground wires attached to the back of cam gear metal rear covers. These are for the "final stage ignition amplifiers"