2018 Impreza sport humming vibration and camshaft position sensor

[Kevin D]

I have a 2018 Subaru Impreza sport that has 155,000 mi on it. About a year ago I bottomed out really bad in a parking lot. The following day when I started the car the check engine light came on. I took it to advance Auto parts and the Subaru dealership nearby, they said it was camshaft position sensor and it was delaying the timing as a precautionary measure. Their recommendation was doing an engine flush because they said there was sludge in the oil supply valve even though I had been running seafoam in the car for years, I started running it at about 20,000 miles in the car. But Subaru and AutoZone said it was Bank One so both sensors on Bank One have been replaced, I replaced the second sensor yesterday, I don't feel the misfire that it was having before, but the fuel economy is compromised. I'm getting about 5 miles per gallon less. It's also making a weird humming vibration like somebody's trying to blow up the left front tire like the air compressor, it also sounds similar to the door stopper that is a spring that dogs and cats like to mess with. But the noise can sometimes last for a couple of seconds up to 10 seconds if not longer. It does it with the air conditioner running, with the air conditioner off, it acts up more frequently on really hot days and we've had several days close to 100° for a few weeks now. The thing that is confusing me that sometimes it will continue to make the noise for about 10 seconds after the car is completely turned off. It sounds like it's coming out from underneath the steering column. The dealership said something about possibly an oil supply valve? I'm not exactly sure, but I like to fix what the problem is instead of continuing to guess. A co-worker said possibly the EGR valve. I'm sure it's a lot of people on here a lot more experienced than I am so any and all suggestions y'all can give I would greatly appreciate.