Car feeling like its starved of fuel

Hi all, i have a 2004 ford focus flight. He passed his mot but then on the same day (yep timing couldnt have been worse) i was driving home and suddenly felt like the engine was struggling to the point it nearly cut out, i had to limp to the nearest layby. After a rest though the car ran fine. Now ive done some work to the car, new cat, front and rear lambda sensors new, back box wielded, air filter, spark plugs, fuel filter, oil change and new filter and flexi pipe replaced this weekend coming. I get a cel saying its the cat, but its brand new, there is a tear in the flexi pipe, could this be the reason? Im leaning towards either new fuel pump 😑🙄 or sucking in to much air. Any ideas?

Also sometimes when braking or high speeds i get a noise that sounds like a flat tyre but deffo isnt, this one is baffling me as its only just started. New brakes, track rod end etc have been changed.