high idle after crossover gasket swap.
 

I have a 98 Deville, one of the coolant crossover housing gaskets was leaking causing it to overheat. Took it off, changed the gaskets, water pump and thermostat. Now she's holding coolant but it did get up to 248 degrees, but she stopped there. But its idling at 1500rpms in park and 1000rpms in drive. Drove it around a bit, drove good other then the rpm, averaged about 2000 cruising. And the temp get'in up there. I had to take the TB, shift cable and fuel lines off to change the gaskets. But everything back on right and tight. Any ideas?

Quick update, its holding water but still overheating.