I dont really see personally why if this manifold was intended for a 4g94 it wouldnt function properly on another 4g94 EPM? ...

whether it was on your car senate and cracked or on the original owners car and cracked , it still cracked , its not a matter of what car it was on ,

lets put it this way if he never sold it and kept using it its safe to say the same thing would have happened on the other car from material or welder defects ...

and yes the flex section always goes on the down pipe usually right in the center under the engine since under torque the engine rocks front to back and vice versa