2007 Subaru Impreza Loses Power When Climibing Up Hill or with added passsengers on board

[zLegend01]

hello good day, i have a 2007 subaru impreza hatchback and anytime i come to a stand still on a hill or i have added passengers on the highway the car loses power and i have to give it more gas to go. i notice the eco light goes off and then comes back on after awhile.

i have changed spark plugs to OEM Subaru spark plugs
i have cleaned the MAF sensor
i have bought brand new 02 sensors
i have checked the fuel pump and see nothing wrong in fuel system
i have clean throttle body
i have checked catalytic converter and is still good
i check battery health and it is at good health but i still lose power sometimes even on highway driving when accelerating in normal or sport mode the eco/sport light would go off and come back on after awhile.
Even with a full tank of gas the car still loses power, and it was not doing this a year ago.

What could be causing the lose of power causes eco/sport light to go off on dashboard and come back on and lost of power?

 

[Ecmbuster]

Make sure all the battery negative grounds are clean and tight. Check all the ground straps as well.
Alternator current output can be checked with an AMP clamp at the battery negative cable.
You need to perform a scan on the engine management system.
Recorded faults can be accessed but with the older SSM protocol, live data can be monitored.
An OBD II tool can be used but doesn't have as many PIDs as the SSM protocol.
The best way to monitor data is to use live screen recording, save it and play the recording back after a road test
Test the fuel pressure and match the pressure to the specification.
Check / test fuel quality for contamination.
Testing fuel pump RPM takes an oscilloscope and the fuel filter is mounted on the fuel pump.
Measuring fuel flow is a good idea with good service tools and not setting the car on fire and proves the fuel filter is not restricted,.
Check / test / clean the EGR valve.
Replace the PCV valve and replace the old rubber hose.
When was the last time the timing belt was inspected?
Is the engine original? What engine model is it? Was there a performance flash installed?

 

[zLegend01]

Make sure all the battery negative grounds are clean and tight. Check all the ground straps as well.
Alternator current output can be checked with an AMP clamp at the battery negative cable.
You need to perform a scan on the engine management system.
Recorded faults can be accessed but with the older SSM protocol, live data can be monitored.
An OBD II tool can be used but doesn't have as many PIDs as the SSM protocol.
The best way to monitor data is to use live screen recording, save it and play the recording back after a road test
Test the fuel pressure and match the pressure to the specification.
Check / test fuel quality for contamination.
Testing fuel pump RPM takes an oscilloscope and the fuel filter is mounted on the fuel pump.
Measuring fuel flow is a good idea with good service tools and not setting the car on fire and proves the fuel filter is not restricted,.
Check / test / clean the EGR valve.
Replace the PCV valve and replace the old rubber hose.
When was the last time the timing belt was inspected?
Is the engine original? What engine model is it? Was there a performance flash installed?

The timing belt was inspected back October 2022 and was in good shape. The engine is original.
Engine model number : EJ20-D174559
As for the performance flash i am not aware that any was installed but with what you said i will inspect each location u said and get back to you with what i find.

 

[Ecmbuster]

Do this test to make absolutely sure there is nothing restricting the exhaust system.
Test 1
Attach a vacuum gauge to a port on the intake manifold.
You may need to remove or plumb into another component temporarily.
Start the engine and allow it to idle close to operating temperature.
Observe the intake vacuum reading, it is your vacuum reading baseline.
A normal gauge reading should be between 16 and 21 inches of vacuum.
Snap the throttle (quickly push and then release).
There should be a brief drop in vacuum as the throttle is opened.
It should return to nearly the baseline negative pressure at idle within a few seconds.
If it takes longer, the exhaust system is plugged.

Test 2
Find a pressure gauge reading: 0 to 15 psi
Find an old O2 sensor and adapt a silicone (temperature resistant hose to the pressure gauge).
Block the vehicle in a safe manner.
Crack loose the oxygen sensor and check the threads.
Loosely Re-install the O2 temporarily.
Idle the engine to operating temperature.
Stop engine and install the DIY pressure gauge in place of the oxygen sensor.
start the engine and note of the gauge pressure reading.
Normal back pressure should be close to zero or 3 psi at the most.
Do not blame the CAT, there may be another obstructions past the CAT.