After finding metal shavings in the oil filter i decided to take engine out and replace the most likely cause which are the main bearings. In the end it turned out i needed a new crankshaft as the original had runout of 0.006mm.

Engine was reasembled with new headgasket, Main bearings, conrod bearing, crankshaft, oil pump, chains and tensioners, oil cooler seals, main seals, waterpump, thermostat and rocker cover gasket.