2002 monte ss fuel surge

i have a problem first of all i've changed the tps the idle control sensor the fuel filter, wires and the fuel pressure reg. the car start and shoots up to full throttle and when i hit the brakes i feel no or little help like there is no vacumm this started a few weeks back when the car would down shift when i floored on the e-way i had to just give it a little gas and it would there i'm thinking the cats clogged but i'm tired of buying parts

sounds like a clogged cat or a monster vacuum leak. What engine?

the 3.8 motor