Okay so I just got my 99 2.5l engine rebuilt by an engine shop and found this threaded hole in the passenger side of the engine and I dont have anything to fit into it. The hole does go through the block so I am thinking some type of sensor. Any ideas?

 

Not familiar with the 2.5L

But only sensors on the block will be oil pressure or Knock sensors
2.5l should have oil pressure sensor on drivers side of block, toward the rear

Not sure if 2.5l even had a knock sensor

 

I'm with ron, definitely looks like an oil pressure sensor hole.

 

Block coolant low point drain.
There is 1 on each side.
3/8" NPT Plug - I'd use BRASS since it is coolant...

Oil Pressure Sending SWITCH is backside of the head - behind the #4 intake runner.