If this is an S with the N14 motor it may need to have the intake valves walnut blasted. On the S with the turbo they are bad about building up carbon on the intake side. They can do it in as little as 35-40k.
is it an S?
My guess it's a non-S because of the comment of 54 psi.....
Non-S gets the valves cleaned with fuel contact, so shouldn't have carbon buildup issues ....
OP should post the engine type or it's going to be a guessing game...
The S has 2 fuel pumps..... LPFP in the tank, and a HPFP mounted on the head....
LPFP runs at about 5 bar (73 psi)
HPFP runs at about 50 bar (725 psi) at idle and 120 bar (1,740 psi) at WOT....
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