Please excuse me!
I just googled the 86 event: Loubet
won GpA! He beat Jean Ragnotti (GpA) by over 10mins. Ragnotti was in a works Renault entry, I suspect.
The list of retirements reads like a who's who of rallying: Mouton, Alen, Biasion, Auriol, Wilson.... and of course Toivonen.
So yes, the GTV6 was clearly very competitive. Of course, Rothmans tended to only sponsor competitive entries back then.