Hesitation on rapid acceleration - 1993 Lexus Ls 400

Sounds like your spark plugs need replaced. ( long shot answer)

CHECK FUEL PRESSURE MUST BE 3.0 BARS AND MUST NOT DROP UNDER 2 .0 BARS AFTER 10 MINUTES.LET ME KNOW IF U NEED MORE INFO AND TELL ME THE RESULTS OF THE ABOVE.

is your saab petrol or diesel?

I'm not experienced in this vehicle, but If you have a hesitation in the gas pedal then I'd be looking at your EGR valve. It may be clogged or have a pin hole in the diaphragm. Look for a broken Vacuum line. Have you put a code reader on the car to see if the ECU is throwing codes? Not all codes will light up the engine light.

The throttle position sensor needs to be replaced.

MOST TIME CAR STUMBLE OR HESITATION ON ACCELERATION YOU.HAVE A SLIGHT LEAN FUEL MIXTURE.CAUSED BY STOPPED UP FUEL INJECTORS OR FUEL FILTER SLIGHTLY PLUGGED.

1-Replace fuel filter.
2-Clean injectors
Most of the time an hesitation on acceleration is due to fuel.

i would try cleaning mass air sensor, its mounted in air duct between air filter and throttle body, they sell the cleaner at auto parts stores, also as stated bofore make sure the intake pipe clamps are tight and it's not cracked, if that doen't fix it i would investigate a fuel pressure problem either a weak pump or problem with regulator

have you checked the fuel injector? if enough fuel is not getting through when accelerating it could "choke" causing the hesitation

Depends how long since your last tune up and mileage. I would do a normal oil change, oil filter, air filter and plugs. If she still does it, try checking for a vacuum leak. Start the vehicle and spray "lightly" carb cleaner around your vacuum lines. If you have a leak the engine will increase in idle suddenly. Replace the line or part. AS A LAST resort and pretty rare is the distibutor. They usually run about 75.00 to 110.00...hope this helps.