S/tb sti cutting out during acceleration

[SuboobaruSF5]

My 2001 sf5 Sti was having issues about a week ago. I got in to drive it and it began (what I thought was) misfiring. I came back home and parked it right away. I looked at some forums online and decided to clean my MAF sensor. The car now can idle without dying and it appears to be okay until I try accelerating and the car is sluggish and seems to cut out at about 4k rpm. My boost is barely kicking in and the car just seems somewhat jerky. While at an idle the A/F ratio is at about 14.4-14.6 which seems fine. I took it out for a drive tonight to see if I could get any more answers but it's still the same. When I got back my gauge told me my A/F ratio was down to about 10.4. I've got some mechanical knowledge but am still in the learning process and I do not own a scanner for a JDM vehicle. Does anybody have any ideas on where I could begin my search. I can't afford a huge auto shop bill and need my vehicle to run. By the way I do have a check engine light on from the incident. TIA.

[rhdgc8]

What have you done for maintenance since you bought the car? Have you put new coils, fuel filter, air filter, plugs etc??
What is the mileage on the Forester? Is it all stock?

[SuboobaruSF5]

What have you done for maintenance since you bought the car? Have you put new coils, fuel filter, air filter, plugs etc??
What is the mileage on the Forester? Is it all stock?

I purchased new iridium NGK plugs but have not yet installed them. I checked the air filter and it is literally brand new so I left it. Nothing else engine wise besides oil and filter change. The car has 120xxx kms on it and as far as I know has not had a new timing belt if you are wondering. (I will get on that after I resolve my issues here) the car is stock performance wise. I bought it used so it could have some small aftermarket tweeks but nothing that sticks out.