To me, the most important thing is to change your ad plan. You are coming along with product, now change up what you are selling, what I mean by this is:
At sites like this, we are so pro-GM that all we talk about are things like RWD, horsepower, etc. But on the street, the other brands are winning on things like quality and company.
So, to me, it comes down to this.
1) Sell the company first
2) Sell the sales experience second
3) Sell the product third
I spent a lot of times in sales, and it was "sell yourself" then "sell your company" and only then "sell the product"
If you can convince people that's it is OK to buy a GM product, then more converts will come over from the other brands. Sell quality, sell how many employees you have that work in the US, sell the advances in technology, talk about the number of gallons of fuel your hybrid busses save, talk about how long you've had on-star, talk about having HUD's in Pontiacs and Buicks, not just Caddies and Corvettes, talk about more vehicles with ABS than anyone else, talk specifically about amount of money you are spending on fuel cells for the next generation of easing our dependence on oil, talk about extensive dealer networks for service after the sale, and on and on.