Land cruiser 2005 V8 looses power when accelerate

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Bought a Toyota Land cruiser 2005 V8 last week. After 2 days of use it started loosing power when accelerate and the RPM will not go above 3 mark. I have replaced the spark plugs, fuel filter, air filter. The throttle and Mass air folw sensor has been checked (replaced to other car of the same model and config to see if it is faulty and the throttle is fine). Throttle has been cleaned. It seems like the last owner has disconnected the check engine sign so can't get the codes. The car runs very smooth if the RPM is below 3 but the moment I press the accelerator (idle or moving), car will vibrate as if the fuel is disconnected and RPM will not go above 3. Another symptom is that at first engine start, car will start and immediately shut down and then starts for the second time normally. Recently I have fixed a leak in the stearing and replace gear oil, filter and diff oil. Car mileage is 190k.