faint knocking sound

[SDBxstr]

hey guys i could use a little help. i have a 01 986 ( love the car) there is a faint knocking coming from the upper roller , i had it diagnosed by ipd here in san diego we both heard it using a stethascope and pinpointed sound coming from upper roller. purchased new roller installed myself unfortunately knock is still there. any ideas your help would be appreciated
thanks mark