Mitsubishi Repair: GDI fuel pump issue, mitsubishi pajero, filter need

Question
While moving off or driving, if I attempt to accelerate quickly (press the pedal to the floor) the engine revs, but not high enough to switch to the next gear, if I ease off the gas a little, the gear will change. When gradually accelerating or in "normal" driving, the gears change just fine (it had been doing this for about 6 months or more and was not getting any better or any worse). I took it to the local dealer for a regular servicing and asked them to check the acceleration issue. The mechanic drove with me so that I could demonstrate the issue then drove with me as a passenger, to feel it for his self. The vehicle stayed in the shop for 4 days, then was returned to me un-drivable. The mechanic is telling me that the GDI fuel pump (mounted on the engine) and the fuel filter need to be replaced. When I took the vehicle in, it was giving the trouble that I described above, but now the vehicle can hardly move. It lurches and then stops repeatedly, even cuts out. The mechanic says that when testing the pump inside the tank, the pressure was fine, but the pump mounted on the engine is not building the correct pressure.

Does the mechanic's explanation make sense or does it sound like he is just not sure what the issue is? Do you have any idea of what the problem is? Could it be the computer not delivering the right signal for the pump to work properly?

Here is the information on my vehicle:
2 Door Mitsubishi Pajero (SWB) Late 1999 model with new shape,
3.5L V6 GDI engine.
Chassie#: V65W0001023
4-speed automatic

Mechanic says it Needs:
-GDI Fuel pump part#: MD367152
-fuel filter


Answer
Leslie: Now look to me that sounds like something more wrong with your the transmission of your car. Well it was before you took it to this shop anyway. I think it sounds like a sensor was getting weak or going out that controls how the car shifts. But now I don't know what this local dealer has done to your car. I would have the car pulled to someplace else for a second thought, well a different mechanic to check the car over. But the problem is that other dealership might have messed the car up so much that it does need all these things. But that sounds like a costly job, I would be asking for help on this bill. I mean the car did run when you took into the shop, but now it won't do that. I am sorry but I have never heard of such a thing, a fuel pump on the engine? But your car is pretty new, so it could be something they have started. I will do a interent check on your car and see what I come up with. Then I could write you again. It is true your computer could be not working right, I think I would want to have the car coded to see if there are any sensors out or getting weak. Just how much will this job, GDl fuel pump as well as the fuel filter going to cost you anyway? Let me check some on the interent. And you see about getting someone else to look at the car and then see if the dealership with help you some with the cost of all this. But because the car did run before you bought it to them and now it will not. See about getting the car coded too. Hope this helps, I shall be getting back to you once I have checked the interent. Linda