Firstly, this is a well made product and looks like it belongs there from factory. I fitted this alongside the short shift, m235 and lower boost pipes so I can’t confirm how much of a difference it makes. However, there are no restrictions in it and it’s a linear diameter. The stock elbow narrows and then expands at the throttle itself. When installing, remove the air filter and it’s the easiest job you can do on the Fiesta ST. Use a flat blade screwdriver to tease away the tightened rubber and it’s twist off easily. Leave the air filter on and you have no leverage to twist it out.
I replaced this at the same time as putting in the Induction kit, ACAI and Intercooler, so access to the bolts was easy. Otherwise, you will need a narrow right-angle with short extension torx driver to undo/fasten the bolts. Now, when is Mountune bringing out a crossover pipe? That seems to be the only narrow point left!
Perfect and easy fitting