ome performance cams do have some lifter noise due to the style of the ramps. Did you check installed height of the valve springs (valve spring noise)? Did you check to make sure that the valve spring retainer isn't hitting on the guide/seal? With the valve cover off start the engine and with a hammer handle put pressure on the push rod end of the rocker. If you have a bad lifter it will quiet down.
Could also be exhaust noise