[crummasel]

If i look to the pics you post here, heads are looking nice but valves seem to be cut much too deep. Could be an indicator that there is no good precaution to concentricity when changing valve guides or generally a bit rude approach.
I had lots US reimports here and motors rebuilt (which were usually redone min once in US) and in any case valve seats were set too deep to allow good valvetrain geometry. (and causing the need to replace all the valve seats, which usually is not necessary).
At least one of the big differences between US and EU Porsche engines if i am looking back on 25 years doing these.
There are possibilities to work as concentrical as possible when changing valveguides andor valves and this minimises necessity to "rescue" concentricity by cutting valve seats too deep.
Just my 2 to consider.