Working on an 03 350z 167k miles AT with the oil pressure reading max (over 120 according to dash) when running. Replaced oil pressure sensor without bothering testing oil pressure because auto parts stores don't rent testing kits & buying it to use only once would be a waste, so I used it to buy the sensor instead, accounting for the age & mileage of the car. Initially, oil would drip from the sensor so I put sealant on the thread. It stopped dripping there, but it dripped on the front of the oil pan instead. The gauge still reads over max. Does it mean that the oil passage is clogged somewhere? I had recently replaced the valve covers & gaskets because cylinder 6 was flooded with oil. The valves weren't sludged & I was very careful scraping off the old RTV from falling in.

Would adding Marvel Mystery oil to the engine be good enough to unclog it? Do I leave it in 100 miles, then change the oil & filter to make sure it's cleaned well? I know you'd normally recommend ATS 505 CRO, but it's not on Amazon & ATS only sells it as a case or fuel/oil 2 pack (cheapest about $70 with shipping & tax, which isn't really practical).

I'd like to fix the oil pressure problem first so I haven't really had a chance to even floor it so I haven't even felt if there's something off with the transmission, but it's got codes P1815, P1759 & P1769 as well. I don't recall which code it was in researching, but I saw a mechanic crack open the TCM to solder a solenoid contact on a G35 from a YouTube video to repair it. If I just got a used TCM from the junkyard along with the solenoids, does it need to be programmed to work properly? Thanks.