If the temp gun says 220 vs 250 as dash gauge reads, that's a big difference for one thing. Not sure why an electric fan was installed? What is the blade count on the engine fan? When sourcing out overheating problems have heard that adding an electric fan can impede cooling as it restricts air flow through the radiator. All else checking I'd take out the elect fan and run it with a (preferably) 7 blade in shroud for another test. Another note is how much modification has been done on motor? Radical timing changes due to mod's impacts engine temp's. My heat sources were quelled by adding 7 blade, (it had 4 blade) a shroud, adding a seal above the rad to reduce air flow miss-direction, reducing the anti-freeze ratio (though you say all h2o now) and adding water wetter. I also reckon you see no entry of coolant in your oil with the checks you've made. Sorry if I've mentioned items already checked or N/A...just tossing out some ideas. And yep, lower hose collapse has been good advice.