I hope this is not too basic for this forum, and if this post should be moved, mods please do so...

I auto-x'd my new-to-me FFR MKIV yesterday for the first time. I'm looking for suggestions on how to keep the rear, well, IN THE REAR! Obviously getting on the gas too hard kicks the rear out, but letting off the gas around turns also makes the rear want to come out even under pretty strong engine braking (which I would think would help slow the rear and keep it from wanting to pass the front). This is a street car primarily that I'd like to feel more confident in while driving it hard that it's not going to come around on me on the street!

I'm going to list the car's specs and post a video of my runs. The camera does not show just how much the rear wanted to slide until that one run where it does a 180 on me. And let me tell you this: the rear was coming out in nearly every turn, especially the big 180 turn mid-course, and when it did come out, it came out fast and was not stoppable (at least not by someone with my skillset ;-)

347cid, T5, 3-link rear.
Koni coilovers, currently with 500# springs up front and 350# in the rear. THEY ARE WAY too stiff for the streets of NY so I have Eibachs on order, 425#/250#.
New Nitto NT01's. I was at about 20PSI all around. For the last two runs, I dropped the rears to 16PSI which seemed to help. The roll indicator on the sidewall showed pretty good, that the tires were rolling to that little triangle.
The temps were only about 70* and the tires never really got over 105* on the outside right front, less on the inside by a few degrees. I'm hoping that was a contributing factor, ambient temp.
I do now know the alignment specs as I just bought the car this winter but it certainly drives, tracks well when just cruising around town aside from how "quick" it turns. I always feel like too much steering input and it'll come around easily on me. I drive with two hands on the wheel like I'm taking my drivers road test! lol

Here's the vid. As I said, even the run where I spin out to me doesn't look bad from that camera angle until the car is no longer facing the right direction! LOL. And you certainly can't tell just how much it's sliding in the other turns - at least I can't. But I assure you, it was.

I'd love to hear input from experts on how to make it handle a bit more predictably.

https://youtu.be/XeZ0zhI_3PQ