I gave up waving several years ago after I followed a black 370z, I flashed him from behind and he responded with what I thought was a wave in his rear view. He pulled into a layby and I duly followed. Parked up and walked over to speak to him and he was on his mobile and looked at me as if to say "what do you want". Wasn't interested in speaking to me at all. Talk about miss reading the situation!!.