KFL007

My friends car makes this noise has been going on for a while. A bm ss was installed on it 1 week it went into a shop for a I forget. He went around to move the car took a awfully long time for just around the block or traffic. Anyhow suddenly the car started making some noise, chattering noise..it sounds like its coming from the console/shifter area. The noise only appears mainly after traveling and letting off of the throttle. I asked a friend of mine he said it could be the throwout bearing? I checked out the shifter again and stuck some extra plastic washer in place of the copper ones. Everything looked tight and not loose. Took it for a drive, no noise for a while..then went over a bump.rattling noise came very slightly..slowing down for a stop..let off.. noise psshh rattle. He's thinking right now of course it might be the shifter so may go stock, but if thats not the problem there goes cash for the stock parts. Any ideas??