hi guys i am daniel from bulgaria.i have a 4 door ford sierra first was 2,0 ohc then 1,6 ohc and the last engine was from sierra 2,8 xr4x4 mfi.the last run of the engine is more than 3 years.i get him in to my sierra and with little work start verry easy.the problem is on high rpm.about 4000 rpm the engine is verry poor and dont rev up.i think is the fuel pump dont deliver the nedded presure to open injectors,warm-up regulator, or injectors.what do you think ?