Employing atmospheric residues when testing FCC catalysts in MAT often faces serious problems with poor mass balances and interrupted operation due to coking of the equipment. When changing to a feed-injection tube made by electroformed nickel (EFNI) in the Statoil MAT unit, the scattering in mass balances was reduced by a factor of four, and the number of interrupted test series was decreased by a factor of two. The reason for the improved results, using an EFNI tube, is the materials lower tendency to form coke, and consequent reduction in clogging.