What are you talking about, you cant just "drop in" a 2.5 where a 2.0 is.
You can if you buy a Contour with a 2.5 put a 3.0 in it.
As for horsepower beyondloaded has a 3L turbo that is going to be pushing over 400hp.
So I guess there isnt really a limit to it, just do all the mods you can to it and you will have lots of hp.
