I'm not sure why you didn't just post why I told you to go meth instead of aux fueling, and why the Boomba kit isn't ideal.
First, auxiliary fueling doesn't give you additional power by adding it unless you are running out of fuel. If you are running out of fuel it is great, but methanol injection gives you more range out of your fuel system as well. I was out of fuel on a 400whp 5558BB Ecoboost Mustang and the customer added my bolt on methanol kit and we were able to reach 450whp and had plenty of room left for fuel. Methanol injection will also give you 2 additional benefits that Aux fueling cannot, cooler charge air temperatures, and octane. Just adding aux fueling doesn't give you any additional octane. It gives you the ability to increase your ethanol content but the highest ethanol content you can run is E85 and it is 106oct and it fluctuates state to state, and isn't consistently 85%. Most fiesta owners are mixing E85 with pump gas, which is a hassle to fill up at two pumps, especially if they aren't next to each other. There is also the guessing game aspect of running mixed fuel. With methanol you don't have to do that, you can fill up your tank with either washer fluid, boost juice, straight methanol, or a mix of your choice and you mix it in gallons outside of the car. For me, I just recommend my customers run pre-mixed boost juice, 50/45 of methanol to distilled water and 5% of other additives like nitro. You can reach up to 120oct with methanol injection, depending on what you are putting in the tank. Is it overkill, absolutely, but you can do it
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Each cylinder in the Fiesta cylinder head gets 2 intake runners. The Boomba aux kit only injects into 1 of those runners, so you are going to have one runner for each cylinder that is going to be prone to carbon build up on the valves. So 4 out of 8 valves are going to be clean, and 4/8 are going to be built up with carbon. Also, port injection angles the injector at a minimum of 30° to allow the fuel to enter the stream and a more natural angle. When you inject straight into an airstream, in this application a pressurized airstream, you increase the chances of turbulence which can change the state of your injection from atomized to more of a solid droplet which is less than ideal.
There is a limit of what you can get out of a methanol kit, and for the Fiesta I believe it is just under 400whp, safely. I hope this helps, if you have any questions please ask.