2.5NA Filter Housing ports

What are the purposes of the ports on a 2.5NA filter housing?

I believe that the brass and steel threaded plugs are for the pipes to feed an oil cooler (if fitted).

From what I can see, the steel plug is fitted on the "to filter" side of the holder. Would it be possible to modlfy this plug to fit an aftermarket oil pressure gauge sensor?

What is the port covered by the diamond-shaped plate held on by the two bolts for?

See attached photo.

Thanks for any replies.

so oil cooler pipes can be fitted ,port holds thermostat for the oil cooler if fitted

Thanks, that explains it.

Did they make these without the oil cooler connections?

Are the plugs usually held in with loctite?

The steel plug on this one was. I was planning to undo the one on the unit fitted to my Series 3 so that I could modify it for an oil pressure gauge connection. However, I don't want bits of loctite coming loose from the threads and getting into the oil system.

not usually

It may be easier to use the existing oil pressure sensor fitting/hole. Less interesting though.