Hi. Just looking for some know how before I head to the dealership. I parked up my 2004 blob eye WRX in my garage a couple of months ago. It was running fine, but had the P0420 code with the engine management light on. It’s only done 78,000 miles & still has its original exhaust, so the dealership said it needed a turbo back system to clear the code for the MOT. I parked it up to save up the money. But now when I started it up, it had a really high idle, maybe 2500rpm, & a misfire. Is that all to do with the engine management light issue, or has something else gone badly wrong in the meantime? Any help gratefully received. Thanks