Please help me with Mustang 5.0l

Greetings comrades, I am repairing a Mustang Mod. 94 Automatic engine 5.0 l, the problem; Erratic march and the engine goes out on the bottom (idle), so I corrected all emptiness leaks, hoses, joints including or injector rings, acceleration body washing, accelerator position sensor check, Good condition, so it changes it and the engine is stabilized totally and in emptiness it works to perfectly has an excellent acceleration and without hesitation lifts the revolutions very well, but when putting vel.drive or reversa, the engine goes out, already calibrates the air flow in the acceleration body, check the terminal 30 of the PCM, which is from the selector of the transmission and in "p" P ". In "R" it gives me 3.8v in "N" 3.0v. In "D" 2.2v. in "2" 1.8 and "1" 0.8v. , which I deduce that there are 5V. of refreence and lower the voltage according to the vel. Chosen for what I think this is not the problem, the fact is that I am desperate because I already changed to spark plugs and cables and the continuous failure, hopefully some friend who has had this type of problem can help me in advance thanks and greetings of Mexico.

Good, you already checked the pressure and flow of the fuel pump, this could be the problem. Greetings from Venezuela.

Thank you for responding, and if you already check the fuel pressure and the MAF signal is also correct, the engine works perfectly in emptiness, the problem is to the mater speed, (mainly "r"), the problem is attenuated by putting vel. and releasing the brake immediately but this does not lend for normal handling. Greetings and I'm still waiting for comments.

Friend already checked that the cables of the masses are not isolated that it used to happen with the corsaes tried to put some additional masses (ground pole)

Thank you, I will check the ground connections and if the doubts I will put additional and comment, and I await some other comments, greetings.