Much better , the xe270 can make tons of power! Its a much more aggressive grind then stock but your gonna need to upgrade your springs to run it. In article in mmff the little xe258 gained 30hp over the stock HO cam on a pretty mild engine combination.. the aggressive ramp rates do make a big difference.
The xe270 is meant for 1.6 RR it has 512 lift. If you want to use your 1.7 RR the best SD cam for you would be the Crowler 15511 . Its a nice cam over stock with a broad HP and TQ range. Im not sure about emissions I think the EFI 270 will pass though you would need to call the manufacture of the cams to find out foresure.