Disco 3 (LR3) Tdv6 head gasket and injector issues

Hi guys.

so I’ve bought another headache.

this one is a 2005 tdv6....purchased with a known suspect head gasket problem......this one is pressurising in the expansion tank.

yesterday when it was delivered with a very flat battery I got it running for a couple of minutes and it sounded fine with no lights on the dash, but it did pressurise straight away.
I had the battery on charge all night and while cranking stayed well over 12 volts.

the engine cranked over for ages,then finally fired up but extremely lumpy (maybe 3 cylinders) and wouldn’t Rev over 2k.

icarsoft gives codes of
p020a
P020b
P020c

injection timing codes.

so do you think the head gasket and injector codes are the same or different issues.

what can I try please guys?
Many thanks

Different issues, pressurising will be head gasket, more likely cracked head, injector codes more likely timing /sensor issues