Oil cooler installed, result
 

My friend helped me install a 25row Setrab oil cooler today (2009 with 1500 miles). We used Setrab oil cooler with a Mocal 180F thermostat sandwich adapter with AN10 lines. Before I say anything, let me start by saying the parts involved are expensive. I honestly don't know why I spent nearly $700, I should have bought the Nissan Motorsports unit instead!

Anyway here are some data.

Before oil cooler 80F
Cruising temp (190-210) 6 gear 75mph
Oil temp after 1st 2nd 3rd redline (210-230)
Idle (190-200)

Post oil cooler 80F
Cruising temp (175-185) 6 gear 75mph
Oil temp after 1st 2nd 3rd redline (195-200)
Idle (175-185)

I expect the temp to come down even more after I put my splash shield back on after my oil change. Other than the ridiculous amount of time and money spent on this thing, let's just say it is worth it if you plan to run the car hard.

From your description, it sounds like you basically DID install the Nissan cooler.
I'm still kind of amazed at how weak Nissan made some of the systems on these cars.
Nice results.

I just had my GTM Comp Cooler installed recently, and did also notice a significant drop in temp, by at least 20 degrees in my case... cooler and install was about $700.

wouldnt having the splash gaurd lower the temps by letting cool air into the engine bay?

The splash pan helps duct the air into the cooler.

I autox the car in humid 80F condition, car never went over 200F and it was mostly around 170-190 all day