We report kinematic shift and strength variability of C iv broad absorption line ( BAL ) trough in two high-ionization X-ray bright QSOs SDSS J085551 + 375752 ( at z _ { em } \sim 1.936 ) and SDSS J091127 + 055054 ( at z _ { em } \sim 2.793 ) . Both these QSOs have shown combination of profile shift , appearance and disappearance of absorption components belonging to a single BAL trough . The observed average kinematic shift of whole BAL profile resulted in an average deceleration of \sim - 0.7 \pm 0.1 , -2.0 \pm 0.1 cm s ^ { -2 } over a rest-frame time-span of 3.11 yr and 2.34 yr for SDSS J085551 + 375752 and SDSS J091127 + 055054 , respectively . To our knowledge , these are the largest kinematic shifts exceeding by factor of about 2.8 , 7.8 than the highest deceleration reported in the literature ; making both of them as a potential candidate to investigate outflows using multi-wavelength monitoring for their line and continuum variability . We explore various possible mechanisms to understand the observed profile variations . Outflow models involving many small self-shielded clouds moving probably in a curved path provides the simplest explanation for the C iv BAL strength and velocity variations along with the X-ray bright nature of these sources .