2013 subaru hesitation no fault codes

im looking at a 2013 subaru outback 2.5i with 161000 miles i believe with a cvt transmission
complaint was that the vehicle hesitates from a stop for a couple of seconds then picks up and accelerates fine
i was able to replicate the problem and i could replicate it every time. at a complete stop i would accelerate at wide open throttle and i would find the car would accelerate very poorly like the engine would bog down it would not misfire it would not stumble there was just a lack of power for a couple of seconds and then the car would finally pick up and go as well as shift out of 1st gear it would do the same thing every time as well. the car has no fault codes and no lights on the dash.
first i suspected there may be a slightly plugged exhaust
i performed a WOT test with the vehicle in park and i noticed the engine would rev up to 4k and bounce off 4k mark on the tach so that tells me the car can see WOT and is cutting off the fuel injectors HOWEVER i noticed the exhaust did not sound as loud as i suspected. the car also had the muffler disconnected as it rusted off at the flange but still the exhaust was fairly quite for WOT.
so i drilled a small hole before secondary cat checked pressure and it was good then i completely removed the 02 sensor from the primary cat did a WOT acceleration from a dead stop and still poor acceleration.
i performed a WOT stall test. engine rpms maxes out at 2k rpms i'm not sure if thats good or bad i cant recall specs
i then started pulling fuel trim data and 02 sensor data and this is what gets me the most. every time i did a WOT acceleration from a stop my fuel trims would NOT go rich shouldn't my st fuel trim max out as it is a command to add more fuel when accelerating and my 02 sensor volts to drop??? i looked at scan data from global mode and through manufacture scan software and same results im not seeing rich fuel trims on acceleration
A/F lambda .90 (@WOT)
A/F volts 2.5 (@WOT)
ST fuel trim 5% (@ WOT)
MAF 40g/s(@ WOT) i inspected maf sensor it was clean
i don't believe i have a fuel delivery problem because the car does accelerate fast if you wait a couple of seconds. so far the conclusion that i came to was that i could be an accelerator pedal issue a transmission issue or the exhaust really is plugged and im not seeing it i know these cars are known for transmission issues like the valve bodies go bad so im thinking it could be something along the lines of a bad torque converter as well so far i believe i don't have enough information to properly diagnose this vehicle

i performed a WOT test with the vehicle in park

This doesn't dynamically stress the engine, it's best practice to put the vehicle in a higher gear, bring it to WOT in a safe area and record the lambda, the ABS ld or CALC ld, the MAF and the RPM at the highest rpm acheived.

"Lambda"

For gasoline fuel, the stoichiometric air-fuel ratio is 14.7 parts air to 1 part fuel by mass, not volume. By volume, that equals 11,000
gallons (or liters) of air to every 1 gallon (or liter) of fuel—a ratio of 11,000:1. If the air-fuel mixture is at the stoichiometric air-fuel ratio of 14.7:1, then the lambda value is 1 (λ = 1).

If an air-fuel mixture has a higher figure—say, a lambda value of 1.05—there is more air in proportion to the fuel than 14.7:1. In fact, it
is about 15.5:1, and the mixture is said to be slightly lean.

A mixture with a lower lambda value, say 0.95, has proportionately less air than fuel. In this case, approximately 14.0:1, and the mixture is said to be slightly rich.

A good engine with good fuel delivery will have:

1. Lambda <1 at WOT
2. ABS LD 80% or better at WOT
3. CALC LD of 100% at WOT
4. At 5500 rpm I would expect this MAF to read at least 110 grams/second

every time i did a WOT acceleration from a stop my fuel trims would NOT go rich shouldn't my st fuel trim max out as it is a command to add more fuel when accelerating and my 02 sensor volts to drop???

We don't really want to see the trims go "rich", we want to verify the AF sensor stays rich at WOT. Fuel trims don't count that much at WOT. IF the lambda is staying <1 that means fuel delivery is good. When you let off the throttle and its in DECEL/FuelCUT Lambda should >1.

I'm not sure which way is RICH/LEAN for your AF voltage. When I'm not sure I drive the sensor RICH with Propane or create a lean condition and watch to see which way the voltage swings!!!

So, if your AF is low volts for a rich condition, at WOT it should remain low volts until fuelcut occurs.

Post some data for us at WOT, i'm curious to see what your MAF will achieve.

I agree with Paul on all counts. While the sensor should report rich, the fuel system is likely going into open loop during WOT acceleration, so the trims won't help you as much as the actual AFR/o2 sensor signals.
The only thing I would add is that every restricted exhaust I have encountered has had the most negative effect trying to reach more than 3-4k rpm.
In my opinion, a "lag" or hesitation on acceleration at low rpm that you can power through is most likely not going to be a restricted exhaust.