I have a 06 6 speed manual xr6 turbo. Over the past 3 months odd it has developed a huge gear lash noise at low rpm sub 1500, and is worse in the lower gears. Gearbox fluid was done probably 12 months ago. Has the usual rattle at idle which disappears with clutch pressure but I cant get rid of this noise even holding clutch pressure unless I accelerate extremely slowly. Any ideas? has anyone run a friction modifier in the oil before as well?