The 07 has more torque in the lower rpm setting than the 05 but the 05 should have more horsepower at higher rpms. Hard to say what the problem is. Was the 07 stock or did it have any mods to increase power (Jet settings, pipes, intake mods?) Also, you can check to see if the long pipes on the 05 are actually TORS by checking for the disclaimer about not being legal for highway use under the pipes. TORS should be louder than stock.
