I have a 2017 Subaru Wrx Sti, car is stock except it has an invidia catted downpipe on stock tune. Car is currently stuttering when trying to accelerate and is only boosting to 9psi , loss of power. No engine lights.

I Just bought a 2019 STI with an R400 Cat back system installed, looking to make it quieter with the Q300 Axle Backs. Very low miles on the system. Looking to trade.

Hey guys! I’ll be installing my catless downpipe probably next week and was wondering if there was an adapter or if I need to use a donut gasket for the downpipe to connect to the Invidia r400. Any feedback would be greatly appreciated.