first suspect would be head gasket / head.
decent gasket used ? elring or payen, if its a britpart one be dubious.
defective new head? overheated new head? (warping / cracking) what make was it?
brand new head or second hand new head?
other stuff but less possibilty would be a cracked liner.
put the stat back in as its a 3 port valve. coolant continually circulated round head when stat shut, when open introduces rad into system.
removing stat allows pump to shift water from rad bottom to pump to rad top......
leaves block and head coolant static........
ejector valve is just a tee peice.
edit.
oh jyhelle, posten on your thread too.