Its been debated for ages.
Some cars with high output ignition systems (turbos etc) and poor grounding from the factory can pickup power with sime earthing.
And if your clio has the groundstrap between box and chassis rail corroded and baout to snap like almost 90% of clios, then itll probably end up running smoother.
But with that kit youll be over grouding between head, chassis, gearbox, bulkhead.....wires all over the shop!