1995 Lexus ES 300 Accelerating

Hi, I recently done an emission test on the car. They said I had to replace cat converter, but I replaced the flexpipe, all the way to the muffler about a month ago so that was kind of odd, but I had them replace it in order to pass emissions. The cat they put it was bigger. They also replaced the PCV valve. Ever since I left the mechanic, acclerating from a stop has never been the same, feels like all power has been lost. Any ideas or suggestions, this is driving me nuts. I did notice quite a crack on the mass airflow sensor hose, could that be the problem by any chance? Please help.