The spin ice compounds Dy2Ti2O7 and Ho2Ti2O7 have come to enormous attention in the past year with the observation of excitations resembling magnetic monopoles. Here we propose to investigate two methods of perturbing the magnetic properties: magnetic site dilution and oxygen stoichiometry. Replacing Dy with non-magnetic Y dilutes the spin system in a controlled manner and has been investigated in detail above 2K. We will investigate the lower temperature behaviour in the spin ice phase. Changing the oxygen content of the samples will alter their structural properties and should affect the local environments the Dy moments significantly. Removing oxygen should lead to dilute Ti3+ ions on B sites which should significantly change the spin dynamics. Measurements will provide data for comparison with previous results on pristine Dy2Ti2O7.