Over heating
 

Got a 91 miata with a 1.8 swap and a custom fabbed turbo kit with aem ems.

Problem is, it keeps over heating, I can drive it bout 10 minutes and it starts creeping past the half line mark. The weird part is that it gets hot, cools down, gets hot, cools down. I figured it was the radiator cap not holding pressure so i replaced that with a 1.4(20lb) but its still doing it. Thoughts?

There are a million threads on this shit from this week alone. Search.

No one here will answer your questions until you search. If they do, I will ban them.

How wet is your water? I once had this same exact problem and I tested my water, and it wasn't wet enough. I was 12% below my desired wetness. I replaced the water with wetter water and now I'm wet.

Does it get hot when you are stopped and then cool down when you start driving? It could be your fan isn't turning on. To rule out the fan, jump testfan and gnd in the diagnostics box to turn the fan on and then go drive around for awhile. This happened to me - it turned out to be a faulty thermistor.

You stand a chance of blowing a hose, heater core, or radiator with the added 7psi of the new cap. That is all I will say due to fear of being banned. Happy searching :)

Ban, ban, and ban.
I'd run with the waste gate disconnected until you figure this out, it might help by eliminating a lot of the turbo heat. Replace the thermostat too, it's another "might as well" part like the radiator cap.