landrover puma blue smoke at 2000 rpm

Hi. I have a 2007 defender puma. At around 2000 revs its puffs out a little blue smoke and hesitates for a second. After that its fine. it starts and drives fine except for around the 2000 rpm mark. I have stripped out the turbo and replaced the egr valve. I have even replaced the valve seals ( and lapped the old valves in ) I really suspect worn valve guides but really not sure. anybody else had the same problem. PS no fault codes appear.