Nissan Micra, 2005, lacks strength.

Hello friends, I have a 2005 Nissan Nicra, diesel 1.5.
He has 190,000km, and began to pull, he lacked strength and evolving, I supposed it was the clut Reprix, it costs him to accelerate, until he reaches 3,500 laps, which I think the injection enters or something, and I notice until the push of strength.
I took it again to the workshop and told me that it is a piece or valve or something, and that the problem was camouflaged by the theme of the clutch.
The fact is that making incorporations to the highway is a real danger because they have no strength, and I cannot adapt my speed in time to incorporate myself safely, or when I take a pronounced or long slope on the highway the car comes low and I am left at 80km/h.

I would like you to inform me what the problem can be exactly, and how much it can cost to fix it, because the mechanic asks me for another € 500 and I am stiff.

Thank you all.

has any failure out? Is there a red or yellow light on the control box when the engine is running?

No, nothing. Neither on the boarding computer either.

I think it does not raise fuel precion, and this failure will depend on what injection system your car has incorporated, if it is Cammon Rail you have a built -up valve in the pump and this is the failure in the common of the cases, if it cannot be the main or electrical pump so I tell you that it depends also if it is equipped with a MAP sensor this can be dirty.

When the car is standing and the engine runs out if you give gas the revolutions rises normal (3500-4000 rpm)? -Other thing, what diagnose machine ascended to the car?-Do you have to put theirs -Consult 2-