Intermittent transmission problem

I recently purchased a used 1991 Nissan Axxess FWD, 5 speed. The vehicle has this intermittent problem (every two days) whereby the vehicle, in every gear, once you reach 2500 rpm's, the car jerks severely and the engine will not go above this rpm. However, shutting the car off and restarting will solve the problem until it returns again. We have changed, mass airflow, vehicle speed sensor, distributor & cap, plugs and wires, rotor, ecm and coil. We have had three different mechanics look at the problem and everyone agrees that it is electrical. We desperately want to solve this problem, any suggestions or have you heard of any similar problem?