The Fiesta ST aftermarket is still developing but with companies like COBB and Mountune at the forefront it still has some impressive options. These companies offer different levels of modification, some packages even maintaining the manufacture warranty while increasing the power delivered from the engine.
Modded Fiesta STs can push over 350 hp without replacing the 1.6L 4 cylinder engine. This might be slightly over the top as the car is front wheel drive and the amount of torque steer increases as the power increases, however, if you’re attempting to provide a race car feel this car can do it.
Each of the Stages are slightly subjective depending on who the source is but there are some rough guidelines for each level.