What is stock bhp? If the tuner is offering you an piggy-back system running different fuel maps I would strongly suggest staying away from such a system. If the tuner can offer you a stand-alone ECU that is the far superior option. You will pay for it, but you won't blow up your engine (if the tuner is good).
With a piggy back system, the tuner needs to either modify the ECU and solder into that and/or run additional wires from their piggy back device to other sensors around the engine, like CPS for example. They will need to "T" into the wiring harness.
With a stand-alone, they pull the OEM ECU, install theirs and you put the original in a dry place at home. You can then swap out the tuned ECU any time you like without issue to sensors or wiring harness.
Those wide fenders are hot man. Specs?