Yours plugged after 400 miles too? Dang...

There has got to be something weird going on here. I had great deltas on the old oil cooler and only replaced it because I was already in there. I'm going to cut open my current coolant filter and see what if anything is in there.

 

You just broke stuff loose in the system when you did the flush.if you can flush the radiator into a big pan a couple times and see what comes out.I would hold my hand on the bottom port and let it fill then release it into a pan.never did get it clean.couldn't hurt to give it a try.id lay odds that you're in the same boat I was.