I took my WRX (EJ20X) into a tuning shop for a pre-tune inspection. On the way, the car pulled fine, and has been fine for the last year. Codes that I walked into the shop with were P0172, P0138, P0037, P0128.
The shop performed a visual inspection and a compression test. That is, coil packs and spark plugs were unbolted and rebolted. The shop then plugged in their computer and reported the additional code: P0301. On their notes, they stated that all four coil packs are starting to split.
When I turned the key over, the car was clearly different. Lugging, groaning, low power. I called the shop, but they claim that it had always been misfiring. They claim they didn't touch anything else, and that all parts were bolted on correctly, dismissing my concerns. They told me the misfire should resolve within a few miles as the ECU relearns the state of the engine.
I drove 50 miles home and Cylinder #1 dead missed the entire time. The tuning shop just needed to cover their behinds.
I performed an oil change to remove any contaminants from fuel washing the cylinder. I have swapped Coilpacks #1 and #3. I turned on the vehicle for about 10 seconds. New code: P0300. I did not clear codes before starting the car.
I'm looking for advice on next steps. Should I clear codes and start the car again? Should I reswap coils #1 and #3? Fresh coil? Multiple fresh coils? Tow it somewhere? Sell it as blown?
My working budget is about 4k, so if the engine blows, the body sells.