99 silverado fuel PSI 47 is that to low?

Hi thanks for looking. My 99 silverado has two codes a P0171 and a P0174. When these two codes register together it is usually a mass air flow sensor or fuel pump/ fuel pump pressure. I just bought the truck with almost 200,000 miles and is still a nice truck. I live in Wisconsin and it has a surging idle especially on some of the colder mornings. I think this idle is because it is a forced lean condition. I have replaced the fuel filter. All Data says it should have 55-60 PSI I had 47 just want to be sure or see what people think before I tackle this one. Probable fuel pump. Thanks.

Admittedly low fuel pressure can cause these codes, have you checked your manifold vacuum ? Vacuum that is unaccounted for, after the MAF sensor, can cause these codes also. Look for any possible vacuum leaks after the MAF i.e. Intake manifold gaskets, PCV valve, PCV hoses, vacuum lines, Idle Air Control valve stuck open, etc.

What engine?

The only true test on a fuel pump is to check the direct fuel pressure from fuel pump.
A quick test is to block off the return line and see if fuel pressure comes up to 75-85 lbs.
But do not run the pump at full pressure very long.
Also when testing fuel pump and pressure you need to tape a gauge to outside windshield or outside mirror and drive it on the road for 20 -30 minutes
until the pump gets has run a while to check for a pump fading out after hot.

Hard to start cold and fuel pressure testing guide line.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
If pump has full pressure with return line blocked and low pressure without it blocked most usually the fuel pressure regulator is leaking or not holding pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure and some 55/62
With a cold start at 60 lbs
Cold start should be 64-65 lbs of pressure or 60 depending on engine.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 55/62 or 60-66 lbs pressure depending on engine load and what engine .
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak in system.
Post back fuel pressure readings.

I would check the cal. on the gauge.. If you really had 47 psi I don't think it would start in zero temps...

pressures as mentioned with engine running should be 60psi plus..
also the surging when cold and the dtc's also as mentioned the vacuum leaks and the throttle body air ducting....

the other thing to do when all this is resolved is to clean the MAF with CRC MAF cleaner....

milwaukee my favorite city [in the summer] I lived there in 1969...

GMs will not run uner low fuel pressure.The 5.3 and 4.8s are known for blowing out intake gaskets and are plastic gaskets