2nd Gear Engine stops between 4-5k rpm

[Focus_Rider]

Hello y'all I'm new here and just got my 1st ST. and love this thing. It is a 2019 Fiesta ST and when I got it it had some surging related issue, at the time was "rectified" by the Ford dealership I bought it from. Well, I've owned this vehicle for about 2 months, and the surging comes after fueling up. WELL today I had something unique happened. Just the other day I went on a roughly 100mile trip no issues. Today I noticed when in 2nd gear and doing a WOT pull or just cruising in 2 and between 4k-5k RPMS the engine. I guess suddenly stops accelerating. It won't die and if I try to push it, it will act like there's no boost, wont do much of anything. No MIL on at this time The moment I shift into 3rd all is fine. No issues in any gear but 2nd. The ONLY thing I have done differently was when I came back home from my trip, I added 4 gallons of mid-grade (mixed it with the high-grade fuel in the tank) I just wanted to get some opinions. I got that ford extended warranty 3yr/36k but with this being my only vehicle atm I kinda want to figure it out before I commit to dropping it off for a week at the dealership.