After removing catalyst the vehicle started, after a month, with a failure that starts around 40mph about 1500 to 2000 rpm, if feels like the vehicle drowns, if the gas pedal is released it goes back to normal but it does it again around same mph's and rpm's. Fuel filter was replaced and keeps doing it. This failure also causes to consume more gas than normal. Air mas flow sensor was replaced too. Check engine signal has never turned on due to this problem. Please if you have any diagnostic for this let me know.