I have a 2018 wrx stage 2 recently i have noticed that under WOT around 5000 rpm the car lurches and hesitates. i can hear minor pops from the exhaust some times. i also am getting frequent feedback knock showing up on my access port. i have replaced MAF sensor. so i have ruled that out as a possibility. the mods done to the car are COBB big sf intake. turbo xs catless 3 inch downpipe. invisible r400 exhaust.