In the engine loom itself on a GT there is 3 i think 3 earth points, one near the ICV on the injector harness, and one near each headlight. These are bolted to the car with 10mm. Then you have your negative earth strap from the battery to the gearbox. And there is another on the OS engine mount. HKS do earthing kits, bolt to the negative terminal of the battery and then put the leads on various points in the bay. Can get em on ebay, well probably reps of HKS kits haha.