Heads/Intake swap finished! Small prob though...

[ultraflo]

I noticed my temp guage wasnt working at all so I checked all the sensors on the lower. There is a small little plug that attaches to a pin on the front drivers side of the stock lower.

sn95gt19 is on the money... if you want your temp gauge to work, you need to hook your coolant temp gauge sender back up.

The cobra had a brass plug in there, so someone took the fitting out. Why did this intake not have it?

I'm going to assume you bought the intake used? If so, then the previous owner might have had an Autometer water temp gauge hooked up in another water port on the intake, and just plugged the hole you've mentioned... just a guess.