Unless someone can physically know what they’ve done, it’s guess work as to what exactly your problem is, but yes, any NA motor shoved straight into an xr6t with the bits whacked on it isn’t a good start.
I know money may be an issue, but save up and take your car to a mechanic or tuner instead of a bunch of people who clearly have nfi what they’re doing or you’ll end up forking our more money on another replacement motor after you blow it up again and again. It’s probably the only way you’re going to get it running properly tbh.
Threads like this remind me of how sad it is these cars used to be extremely desirable, expensive and usually looked after.... now they’re the new VN crappdore 😭