R33 S2 Gtst Boost And Overheating Issue  

Ok I've got an R33 S2 GTST , it overheated ( & cut out won't start again), yet to have it pressure tested but seems to be leaking from the water pump ... But still not convinced it's the head gasket YET. No other obvious leaks when it first over heated and steam come more from back near fire wall rather than around the radiator or front of the car . Oil looks ok not milky .

Question also is I have a HKS EVC-S boost controller & usually sits at file reading - 73 and now sitting at -64 at idle . For this to happen , could it be due to say a vac hose maybe or would it manually have had to been adjusted ? ( reason asking is that there is a chance this was done manually without being advised ).

Since this has changed it started to backfire occasionally under boost and after a while ( 1000kms) it's overheated .

Just wanting some feedback and anything I can check prior to being pressure tested properly of course to determine whether it's the head or not