I passed ma state inspection with a catless downpipe. I put my stock sti cat back back on the car, however. As long as your ecu doesn't throw a C.heck E.ngine L.ight for it being catless, you should be fine. I believe that a stage two map from your accessport will take care of that. Also, I do not reccommend flashing a tune that your car is not set up for.