Before the swap, my car would stay steady at 220 when it reached that temp (pretty much like you would expect). After the swap, the temp would stay low but after about 4 minutes of driving it would shoot up to 260 in a matter of seconds. It's definitely not the thermostat, I even ran it without one and it did the same thing. I have a mechanical fan, so it's definitely working. The only thing I can think of is that the new intake (Performer #3706) has rear cooling ports, and my old intake had them blocked off. The gaskets I used had the rear ports blocked off except for a small hole. My question is has anyone else had this problem and if so, how did you fix it? I included some pics of what I'm talking about.

 

You have air trapped in the system. Try running it up to operating temp with the radiator cap off. Keep an eye on the coolant level and add as it goes down.

 

That must've been it, thanks!