2019 manual transmission Subaru Imprezza skips lacks in acceleration

I drive a new 2019 manual transmission Subaru Imprezza. Started driving her five months ago. She’s only had one oil change. Synthetic oil before and after the oil change. She’s been stalled less than 5 times total.

I noticed a few days after the oil change, on an uphill incline, she was skipping in acceleration. I was cruising in 5th gear, then dropped it down to 4th thinking she was simply losing power, then she started really dragging in 4th, and 3rd, and in 2nd gear. I parked her that night, next day she was driving fine.

It’s now happened on and off in the lower gears, where she’ll skip/won’t accelerate/have a hard time accelerating, while I’m pressing the throttle down. I have yet to determine what the common denominator is, and what causes the skips. I feel it most uphill, and when I’m really trying to go. I never press the pedal all the way down. I don’t ride the clutch, parking brake is off.

No lights are on, nothing’s leaking, oil level is fine, no codes are being read. I took her back to the dealership, and they reported nothing back. The only thing they could offer is for me to leave the car at the dealership for some-odd days and go from there.

Any thoughts? I’m convinced it’s computer related and not altogether engine related. I need something to present to the dealership, give them something to look at.