Saturn lacks power top speed is about 45 mph what could be causing the problem? on 2002 Saturn L100

there is no check engine light on. Dealer service center
did a diagnostic and said the converter may need replacing
muffler shop said it was ok. Replaced coil pak, plugs,
throttle position sensor but still have the same problem.
High rpms changing gears (auto) lacks power will not run over 45 mph

Asked by for the 2002 Saturn L100
have you changed the fuel filter?