When the series 1 intake goes (and it'* rare), it'll be on the passenger end, where the coolant bypass hose enters. There'* a plastic fitting that breaks on the hose where it enters the intake, but sometimes it can damage the intake itself at this location, too.
It'* plastic, so it'* possible to damage if it gets too hot, nonetheless. The 180 stat should help.
I'm betting your thermostat isn't opening fully, or is partially restricted. Is the rubber o-ring installed right? The paper gasket? You may want to buy a higher quality tstat and swap it out again.