LOL. You're telling me. Working on my car has always been difficult and frustrating. I had sort of the same issue as you and did the EPAS swap from a 2014.
Could be a tooth broken in your rack and pinion. Have you ever had the steering shaft out? You could have put the bolt in backwards when you reconnected it. I'm talking about the bolt that locks the steering shaft into the rack and pinion. On one side there are threads, on the other side there...
I had this same issue when I got mine for dirt cheap. I found the parts list on the instruction manual for the manifold.
https://performanceparts.ford.com/download/instructionsheets/FORDINSTSHTM-9424-463V.PDF
2nd page. Get some Fel-pro gaskets too...