parts costs for any car , on earth are not the same all over earth
not even close, .
unless in N,Korea or Cuba.
new, used , rebuilt
beside the mount error
all those error could be just 1.
even vacuum leak.
P0300 says all cylinders misfire so there other P030x error are pure redundant.
cam sensor is serious, in the real world that cam sensor error is very serious. and causes misfire, so misfire is expected
why add up cost when you've no clue what is bad.
OBD2 DTC are just the starting point of diagnosis
the PCM is not AI, not by a country mile ,even to the moon.
we cant watch you or the car ( in the secret act)
did you crank a dead engine so LONG, that battery went low and now all computers in the car are telling lies, and is common as nails now. this effect..
no symptoms told at all just a DTC dump.
no engine told at all and A4
4.2 L V8 40v DOHC >< complex this.
seems it is just 1,
posted ANON so no other way to know what engine is here.
nor there post full of symtoms not told here
and what happened the day this all started.
engine died? what?
starter cranking slow is not good,
step 1 on all cars , we keep the battery fully charged till the engine starts to run and stays running and battery volts are 13 to 15vdc,
a volt meter tool find that easy.
if below 13vdc the alternator is dead or its fuses.blown.
also we do not sell engine parts. here. just free advice ,just that.
no miles on the car told, over 90,000 miles
and the silly cam belt failed. making CAM sensor go dead?
the belted cams can not be ignored
the belts are changed out at 90k miles 140km
https://www.rockauto.com/en/catalog/audi,2005,s4,4.2l+v8,1430752,engine,timing+belt+&+component+kit,5759
good luck , DTC codes are not AI, not at all