After reinstalling #2 engine exhaust plug and torquing the attach bolts; Mechanic notices the exhaust plug still had a slight movement when pushed side to side and up or down on a B757-200. Aircraft was released for service.

Narrative

In January 2009; reinstalling exhaust plug on #2 engine (after removal by third shift) per Aircraft Maintenance Manual 72-51-01; using torque values in Aircraft Maintenance Manual reference 70-51-00; the exhaust plug did not tighten completely after torquing exhaust plug bolts. The tip of the exhaust plug had a slight movement when hitting the exhaust plug with my hand side-to-side and top-to-bottom; approximately 1/8 inch or less. I was not too concerned; because the plug bolts were torqued; and the movement was not that great. I felt the plug would not separate from the engine. The thought of the plug being 'loose' stayed in my mind and my concern grew. Upon arriving at work Jan/09; I reported this to my Maintenance Foreman. Took the pertinent information and said he would talk to Maintenance Control. The aircraft was on the gate and was to depart approximately XA00. I went to the aircraft and checked the exhaust plug and no change was noted. The aircraft RON ZZZ Jan/09 night and will have further evaluation. I wanted to self disclose to possibly prevent an event from occurring. Not taking the time to troubleshoot the cause.