GMC Acadia 2008 not GDI

Acadia 2008 v6 not gdi 
NO CODES PRESENT AND CATS ARE NOT CLOGGED. I checked those things. 
I am struggling with a gmc Acadia which has poor acceleration or low power when accelerating. Car dos not misfire. What I did is went for a test drive and press the accelerator at full throttle and I saw that the o2 sensors instead of going rich, they go lean so that is telling me a fuel problem delivery. Correct me if I’m wrong.
so what we did is checked the fuel pressure. At idle it’s between 56-62 which is normal but when I go full throttle driving it drops to 25 psi in a period of 5 seconds. 

I don’t know what’s wrong and it does have a new fuel pump that I installed. I’ve never seen this kind of problem before so if someone can give me a little help would be awesome. Thank you and have a great weekend. 

 

Can you get the fuel pressure to drop while power braking in the service bay?

If so, I'd monitor current on the Fuel Pump 15A fuse in the underhood fuse block at idle and during the power braking. I'd expect 8-10A of current from this pump. If you maintain good current flow but lose fuel pressure, that'd suggest there's something wrong with the new pump. Or, possibly a pinched fuel pressure line? Unlikely but still possible.

Low current flow would indicate a pump circuit issue. You could voltage drop most of the pump circuit at X305 (where the tank harness plugs into the body). Again, with the low pressure present, I'd expect less than 300mV drop on pump power or ground. More than that is a red flag.

No, I can’t! Only drops when i go full throttle and the vehicle is moving.

I guess I’ll have to do that while the vehicle is moving.

Another thing, I’ve heard that this Acadia have a fuel pump module located by the charco al canister. Is that something to take into consideration as well or not ?

Will do that and get back to you. Thank you 👍😎

This is at idle
I have 13.7 volts on the harness conector at the fuel pump and the ground is 0.1 volts.

Fuel pump is drawing 2.14 ampers of current ! Is that for sure that the fuel pump is bad or is there another possible problem on the harness somewhere?

Another thing, I’ve heard that this Acadia have a fuel pump module located by the charco al canister. Is that something to take into consideration as well or not ?

I checked the wiring diagram for an '08 Acadia yesterday. No module, just power from the fuel pump relay and a ground.

I have 13.7 volts on the harness conector at the fuel pump and the ground is 0.1 volts.

Do you recall which pins you were on? Should have been A and C, grey and black.

 

Asking because there's other circuits (vent solenoid, fuel tank pressure sensor, level sensor) in X305 that also have power and ground.

Fuel pump is drawing 2.14 ampers of current ! Is that for sure that the fuel pump is bad or is there another possible problem on the harness somewhere?

That's definitely low. You're on the right track.  If you're confident that you voltage dropped the correct pins at X305, then you're down to high resistance in the fuel tank subharness, or the pump. Tank is coming back down either way.

Do you have a headlight or alternate load you can use to test the subharness once you get the tank down?

so yes i was on those pins. Black wire which is the ground (0.1v) and grey wire (13.7v).
so you mean to use the headlight as the fuel pump in this case?
and what should i see? ill do that tomorrow and get back to you