I can't imagine how you could "improve" Guinness by adding anything to it:shocked2: The sacrilege! Sounds a bit like saying "Hmmm, I'm going to see if this Dom Perignon tastes any better if I add some brake fuel to it"...
I agree that Guinness can not be improved. However it can be used to improve other beers.
You can't do a Carbomb without Guinness. And have you ever tried a Guinness float?