Just finished rebuilding my turbo 2003 NB
car had a complete rebuild with a 3 shim boundary oil pump. Went ahead and switched the stock oil gauge out with an AEM and the car is stuck with low oil pressure. At my absolute wits end trying to figure out why. At idle and warmed up I’ll see about 6 psi. 3k will see 20~, didn’t bother bringing it higher than that.

is my oil pump already to blame or is there some other culprit that will keep me from throwing away all my time and money and tearing the motor back down?

 

I like to confirm oil pressure issues with a mechanical oil pressure gauge. Excessive bearing clearances or the cylinder head restrictor was not installed. Possibly the oil pump, but usually they stick the relief shuttle and the result is 0psi at idle. You might pull some of the oil and visually inspect it for contamination/wear materials. Not a fan of the boundary pumps because of the cheap chinese ITW castings. Most likely you will have to pull it apart.

 

Reversed oil feed to a remote filter? Don't ask me how I came by this titbit ...

 

What's the oil pressure, cold, at 3K RPM?

 

not to sure, I know cold the pressure would idle around 12 and start dropping as it warmed eventually settling around 5-6 psi max. We are a little reluctant to start it back up and rev it for obvious reasons lol

 

Well, if it looks good when cold and rev'd, probably a stuck relief valve. Happens on aftermarket oil pumps.

 

Verify with another gauge, then start removing the engine. I spec bearing clearances and oil pump, somethings dumping oil. Were the squirters installed? Pickup tube torqued? Etc.

 

I would also do this. I had a bad aem gauge that would end up reading 30 psi over what it was reading. Got a new sensor and it was all good

 

I would also question the gauge first.

As a reference point, I think I have the same oil pump as you (boundary stage 3) and I'll see about 60 PSI on cold idle and closer to 20 after an autocross run when running 15W-40 oil