Ok, new to the forum, having a problem I can’t find a cure to. About three weeks ago, my wife’s Legacy started surging. It started with a P0420 code on the Cat. Thought maybe O2 sensor so started there and replaced both. Problem persisted and same code popped. Went to replace the cat, and it had been punched out (branded/salvage title). New cat didn’t fit, so I went ahead and threw some non-foulers on the downstream sensor to fool it into thinking the cat was there and working. No more codes, but still surging. Thought maybe a fuel delivery issue so I changed the pump. Didn’t do the filter though but that’s probably gonna be next. No dice with the fuel pump but the problem persisted. The freeze data showed a throttle position problem. Put a new throttle body in but still surging. In park if I revv It up to around 4K it’ll stutter/surge. Under load it pretty much does it from the get-go and I can’t get it above 30-35mph and it stutters violently. I’m kinda at my wit’s end with this car. Any ideas??