Hi All. Have the 2005 Sirion 1.3 L K3-VE I4 for about 5 years now. Very satisfied up until 6 months ago. Had the engine overhauled - replaced everything with new, pistons, oil pump, water pump, thermostat etc. Mechanic stripped one of the head bolts (never said anything) but was picked up when i had the radiator tested because the car started running a bit hotter than usual.
This was also then sorted. However since then i get really crappy mileage as the car is running very rich (lots of carbon coming out of the exhaust). It does not miss or anything although the idling seems to hunt the whole time. Have had the car on a diagnostic and all it showed was a pressure warning because of the head gasket. This was cleared and hasn't come back.
Taken to 2 other workshops and they also just ooh and aah'ed. One did mention a vacuum leak somewhere might be the cause?
Would appreciate any thoughts or pointers you may have.

Thanks
Peter