cyl 1 30psi is very low, and i would have thought a noticable fault, very likely a poorly seating valve, but you would have thought the engineers might have picked up on this depending on what the technician asked them to do.

we generally send heads away for resurfacing and pressure testing, If he only asked them to resurface it then there's no reason they would have had to touch the valves.

either way it sounds like the head has to come off again, assuming the hydraulic lifters are in good order and not stuck open.

generally speaking when rebuilding these engines, if the lifters are going to be used again we make sure the oil is squeezed out to ensure they dont hold the valves open when trying to restart the engine.

it can take a while to get oil back into them, and often they run rough, if at all until this happens but its much better than the valve being held open when it should be closed for obvious reasons.

A simple compression leak back test would narrow it down,

Cheap testers cost around £30 from Ebay and the results are definative!

I'm supprised your tech hasn't got a tester,

No mechanic wants to waste their time and your cash on gueses!

It works by injecting air into the spark plug hole,

and a guage shows the cylinder holding pressure,

If 100 psi goes in and holding pressure is not 100 the escaping air can be heard where it's coming out,

Intake would be inlet valve,

exhaust would be exhaust and so on...

One other thing that seems to have been overlooked,

the camshaft it's self,

if the lobes are worn they will not open the inlet valve long enough to draw air in to be compressed!

Just a thought.

Get your tech to buy a compression leakback tester.

One question though,

Be exact,

The engine size and type would be the most help,

I.e is it an 16XEP?

Reason I wanted the engine code is I had a spooky similar experience.

Head off,stripped and sent for planing.

Pressure tested and valve sealing checked and passed.

Rebuilt it only to find low compressions!!!

And after much testing,

re testing.

head scratching and eliminating evert possible,

i took out the cams,

compared them,

looked identival

BUT!

After checking thr Vaux TIS manual realised I had fitted the cams/sprokets the wrong way round.

Timing tools fited even though.

So re fited the cams so on TDC No1 the inlet cam lobe was pointing to the rear of the engine.

EX cam lobe cyl 1 pointing towrdas the engine front.

And if I rember right inlet lobe 2 pointing up and slightly to engine center,

Ex No 3 lobe pointing up and slightly towards engine center,

THEN FIT THE CAM LOCKING TOOL.

turned ke and brooooom!

Like I stated at the start of this,

all this sounds sooo familar.

Maybe your mechanic,like me,removed the cams and caps and followers before seding it to the engineers.