ICRF power levels of up to 2.8 MW were achieved during the 1988 experimental run on TFTR. Metal impurity concentrations (Ti/el, Cr, Fe, Ni) and Zeff were monitored during ICRF heating by X-ray pulse height analysis and UV spectroscopy. Antenna phasing was the key variable affecting ICRF performance. No increase in metallic impurities was observed for Pr.f.<or approximately=2.8 MW with the antenna straps phased 0- pi , while a measurable increase in titanium (Faraday screen material) was observed for Pr.f.>or approximately=1.0 MW with 0-0 phasing.