Ok a bit of a recap and starting from the top .. you got the car started , i assume no obvious misfires .. car ran ok ?
Ignore the comprsion checks .. they are low , several cyls very low which would give you a running fault , misfires etc , you dont seem to have that .
Compresion check needs fuel pump fuse out and even so you can still get bore wash from residual fuel injected and as you know .. throttle open is best .
Rule of thumb , even running then all cyls ok reguardless of compresion check , no lumpyness then its ok basically .
Crank sensor .. usual fault is engine stops when it gets warm , will restart after 10 mins or so .
With car in the non starting position you need a noid light on any injector to see if you have switching .. ie crank sensor fault .
Spark , a little harder but a spare coil and plug , connect it , ground the plug and crank .. do you have spark .
Fuel pressure , the pump can get blocked , more so on 997 but even so , theres a filter in the base , it can get restricted , check is with gauges im afraid , no other way .
Fault code check .. this is the first thing i do to be honest .
Single plug replacement is usually a sign of a mechanic diagnosing a fault , replace a coil or a plug .
I very much doubt it but unplug the maf sensor and start it .. if faulty then it will reset to defaults and run ok .
Exhaust in coolant ..
If compression gasses get into the coolant via a crack then you will have a serious over pressurisation of the coolant system , the cap when released will shoot out coolant even when cold after a few mins of running , a " sniff test " , chemical test will prove that very quickly , but ..
unless coolant gets into a single cyl then it wont cause running issues .
Plugs all the same " colour " then you dont have coolant in cyls .. black = over fueling .
Heavy buildup = oil leakage into cyls ..
White or pinkage can indicate coolant .
Remember .. you bought a project , you have the info .. play and fix .. dont give up , its fun when you fix it ..
Also .. i do this every day lol .
Thats all i got for now but keep at it
Ignore the comprsion checks .. they are low , several cyls very low which would give you a running fault , misfires etc , you dont seem to have that .
Compresion check needs fuel pump fuse out and even so you can still get bore wash from residual fuel injected and as you know .. throttle open is best .
Rule of thumb , even running then all cyls ok reguardless of compresion check , no lumpyness then its ok basically .
Crank sensor .. usual fault is engine stops when it gets warm , will restart after 10 mins or so .
With car in the non starting position you need a noid light on any injector to see if you have switching .. ie crank sensor fault .
Spark , a little harder but a spare coil and plug , connect it , ground the plug and crank .. do you have spark .
Fuel pressure , the pump can get blocked , more so on 997 but even so , theres a filter in the base , it can get restricted , check is with gauges im afraid , no other way .
Fault code check .. this is the first thing i do to be honest .
Single plug replacement is usually a sign of a mechanic diagnosing a fault , replace a coil or a plug .
I very much doubt it but unplug the maf sensor and start it .. if faulty then it will reset to defaults and run ok .
Exhaust in coolant ..
If compression gasses get into the coolant via a crack then you will have a serious over pressurisation of the coolant system , the cap when released will shoot out coolant even when cold after a few mins of running , a " sniff test " , chemical test will prove that very quickly , but ..
unless coolant gets into a single cyl then it wont cause running issues .
Plugs all the same " colour " then you dont have coolant in cyls .. black = over fueling .
Heavy buildup = oil leakage into cyls ..
White or pinkage can indicate coolant .
Remember .. you bought a project , you have the info .. play and fix .. dont give up , its fun when you fix it ..
Also .. i do this every day lol .
Thats all i got for now but keep at it