Coolant overflow weirdness

Since I fitted the fmic and had to drain a bit of coolant out to clock Turbo, the aftermarket aluminium coolant overflow bottle keeps spitting out small amounts of coolant when driving. . I topped up the header tank and let the air bubble out, then too up from the Rad cap and added a bit to the overflow bottle. Does this mean there is still air in the system and I need to do a full drain or possibly something else causing this? Never done a full flush before myself so not sure how to do it.

Sounds like you have still got air, there is no need or benefit to draining the system, as you will end u[ in a worse situation than you are now...

If possible try filling the Tank from a height, using some rad hose and a funnel, this should do the trick for you

Cheers Ken, got it sorted was just loads of air in it still, i didnt bleed it right after topping up. all grand now