Recent XMM-Newton and Chandra observations of the gravitationally lensed BAL quasars PG 1115+080 and APM 08279+5255 have provided new insights into the structure of quasar outflows and the enrichment of the intergalactic medium by quasar winds. The confirmation of relativistic outflows in most quasars would imply that these energetic winds have a significant impact in regulating the growth of the black hole, perhaps explaining the M BH-σ relation, and halting star formation and shaping the evolution of their host galaxies. We present new results from multi-epoch spectral analysis of BAL quasar PG 1115+080 with XMM-Newton. We find significant variability in the properties of the outflowing absorbers. Relativistic outflow velocities are inferred from the blueshifted highly ionized Fe lines detected in our analysis of the EPIC spectra. The depths of the Fe X-ray BALs in PG 1115+080 show a significant decrease between the first two observation epochs. We constrained the fraction of the total bolometric energy released by quasars PG 1115+080 and APM 08279+5255 into the IGM in the form of kinetic energy to be ε k= 0.3 -0.2, +0.1 and ε k = 0.09 -0.07, +0.03 respectively. According to recent theoretical studies this range of efficiencies is large enough to influence significantly the formation of the host galaxy and regulate the growth of the central black hole. An analysis of the RGS spectra indicates the possible presence of two absorption lines at rest-frame energies of 3.36 keV and 3.73keV.