I have a 2002 toyota corolla s and i recently had the cat converter replaced. We thought that was going to fix the little flutter i would get sometimes when i would push on the gas to get going. It is like it does not grab the gas or power. After i replaced the cat converter the fluttering is now worst. Every time i come to a stop and try to get going again it will hesistate and all of a sudden it will pick up and zoom i'm on my way or even if i slow down a lot to take a curve the same thing. We've done a whole fuel system cleaner and checked the fuel pressure and it's all ok. We've cleaned the throtter in case it was dirty but no luck. spark plugs are new as well. We thought of replacing fuel filter and contacted dealer to get the part since auto parts store didn't carry it for my car and found out my fuel filter is non-serviceable since it is in the gas tank. We are running out of ideas at this point. anyone have suggestions?