2001 Chevy Impala

Hey guys, I really hope you can help. I went to Florida with my car and it put some work on it driving all those miles from Maryland. I went to my local mechanic who does all my work and had them change my spark plugs and plug wires. Also a fuel filter and air filter. The car takes off slow like its not getting fuel then after I hold on the gas it will get up to speed, after I get it up to speed and get up to about 50 mph it will sound reved up high like its gonna blow up. Last time it did that the check engine light came on and flashed and for my car the manual said flashing means emissions issue, but my mechanics checked the Cat. Converter they said no obvious issues put it on tests and the whole nine yards. I have never ran out of gas or used a different octane. Always up to date with oil changes and preventive maintenance. I even put fuel system cleaner in it.