TLDI low compression. Please Help!

Hi all i need some tech help! I have a 2002 50hp tldi (MD50A) that runs and seems ok power wise but has a mis or sneeze at mid to low rpm. At wot it sounds normal. I done a warm compression test and all 3 cylinders are 70psi. Also decarb the pistons and basicly same reading. The motor only has 60 to 70hrs on it according to ECU so I'm thinking it has sat for a long time and rings are seized on piston possibly? I can see some oil bubbling out of bottom injector when idling but I think that's a separate issue.
Would appreciate some help on next steps to possibly diagnose this issue!

Am I correct in thinking the only fail areas on tldi for low compression are rings, head gasket, injectors, spark plug and reeds?

Yes. Any codes?

Yes, both water temp over heat codes.

I did noticed a steam sound coming from engine just before it stalled last time out. It would restart after about 5min. However it did not throw a code on that occasion.?

Are there any more tests / checks I should do before I start tearing this motor apart?

Check fuel and air pressures.

So I have pulled the head and head gasket all looks good. Each bore looks and feels smooth however visually looks like it has some rust on bores at some stage but feels smooth to touch. All piston tops look fine. Will try upload photos.

20210507_121840.jpg

Need Following parts for this tldi MD50A. Year 2002.
*Piston ring kit.
*Full gasket kit. (Head, crank, intake, air manifold, ect.)
*O ring kit for all injectors.

Having trouble finding parts for this engine. Please help.

3T5 871230 ring set 85.23
3T5 871218 power head gasket set 140.00
3T5 103040 o ring
3T5 103030 o ring