You need no diagram ( i think). You need to chek round socket upper alternator which connect entire injector wiring with the part of wiring under intake manifold (injectors, TPS, idle regulator and other). Connector use rotating lock and very often it does not locked as it need to be.
If you need this and other diagrams you simply need OPEL TIS - some sellers on ebay sell such CDs but because of ebay rules they called such CDs "manuals" or they use other such words. But inside is normal TIS. Or you can download it from internet.