Nope the boiler would've been shipped with an orange plastic cap blocking the expansion vessel connection. I would say the OP is probably right and there's been air trapped in a couple of the rads.
Will be interesting to see how you get on as constantly running at higher than expected pressure won't have done the tupperware boiler any favours
Will be interesting to see how you get on as constantly running at higher than expected pressure won't have done the tupperware boiler any favours