2013 Subaru forester is throwing a PO351 code.

This is Bo, an auto expert on RepairPal's Car Genius team! Even though you’ve replaced the spark plugs and coils, I’d recommend taking a close look at the wiring and connectors for cylinder 1’s coil. Sometimes, a loose connection or damaged wire can cause this intermittent problem, especially if it shows up after driving for a while. There should be a brown and white wire present where the coils plug in. Also, check the Powertrain Control Module (PCM) connections; heat can sometimes cause intermittent faults there. If everything looks good, it might be worth having a professional scan the system in real time to pinpoint the issue. One more heads-up: Subarus can be finicky after disconnecting the battery. Make sure to let it run and reset it's idle before driving it If you have any other questions, please call us at 877-913-1554! We'll gladly find you a certified RepairPal shop in your area!