2000 Plymouth Neon acceleration help!? checked everything HelP !?

i have given my car a full tune up oil change spark plugs wires filters timing belt recently had the tire rod and wheel bearings and brakes replaced ... yet my car still has such horrible acceleration... its been checked on a pc before at my mechanic and no bad codes showed up ... is my car running bad or is it just me being crazy and not used to the slowness ?