The leaks regarding the 2011 Mustang GT's (the V8 model) engine specs have the previous 315hp engine being replaced with a 412hp engine. It'll still get about 24mpg highway though. On the other hand, the V6's 210hp engine is being replaced by a 305hp model 2011. And get this, going from 16/24mpg to 19/30mpg. (Those numbers reflect the automatic transmision model.)
As for GM, it was the reintroduced 2010 Camaro, especially the V6 model which currently has comparable numbers to the upcoming Mustang V6, that really spurred Ford on.