This sensor maybe on or near the air filter, or on the fuel pump module. It looks exactly like a map sensor but its job is to monitor the evap system pressure. Im surprised the dealership mechanics are not following the correct flowchart tree to fix this.
Its very very simple and cut and dry repair job, very basic back probe tests and a final check by artificially applying vacuum to it on a bench. Finished off by a smoke test of the evap system intact.
circuit performance usually indicates that the reading is out of range which can be a myriad of issues. Its a basic 3 wire sensor and is very simple to troubleshoot.
Are you topping off the fuel filler when refilling fuel - meaning filling it to the very top of the filler like filling a bottle or letting the fuel filler click itself shut? Topping off the fuel to the very top can cause a lot of extremely costly issues.