Lexus with no power

i have a 1992 lexus ls400 that everytime i try to go on the freeway or step on the gas hard the car would choke. i had replaces the trottle, the timing belt and the muffler but noting works . what might be the problem.

Have you tested the vacuum? Is there back-pressure at the catalytic converter? When was the last time a basic tune up was done?