Slant 6 oil pressure woes…

Charrlie got to this first, but if seven quarts is "full", something has to be wrong. As others mentioned, full is five quarts unless you have some oddball racing hi-capacity pan. I'm guessing you either have the wrong dipstick or it's mismarked. To verify your dipstick is correct, drain the oil and put a new 1-qt filter on it like the WIX you were using. Add four quarts of oil and start the engine, letting it run for a minute or so then shut it off. Now the filter is full. Pull the dipstick and check it - you should be at the "add" mark. If not, make a mark for the new - and correct - "add" mark. Add one more quart of oil, you should be at the "full" mark. And again, if not make a new correct "full" mark.

All of this is assuming you don't have a huge buildup of crud in the pan, which would throw off your measurements. If you're going to pull the pan and check the pickup, the above should be done after that process.