My 2c,
I had intercooler heat soak issues a couple of times in my previous SW20 as it went through it's different engine setups.
When i had a stock motor with a Greddy T67 hanging off the side running a Power FC, Pump, injectors, exhaust etc I used a Greddy copy intercooler with the metal shroud/plate to seal it to the air vent and a fan shroud with an ATS 8 or 9in fan on the engine side of the intercooler. Also custom heat shielding on the tubular Greddy manifold.
On the dyno it got up to just under 250RWKW but was heat soaking pretty bad. They were letting it cool down for a while and then going again. Eventually the engine broke (3 of 4 pistons) which could be down to the hot intake air and the tuner struggling with this. It was a mad turbo though, came on boost like a maniac. Yep still drove it for a whole with broken piston ring lands.
Rebuilt that motor into the last engine the car had with 316RWKW from a GT35R at around 20psi from memory.
I built the intercooler myself which was boot mounted, 700mm x 300mm x 100mm (huge), 2 x 12inch high volume fans, holes cut in the boot floor for the air to escape and modifications to let cold air enter from the wheel wells.
This intercooler never went a few degrees over ambient air temp ever to my knowledge. It was truly an overkill setup.
If I had to install an intercooler again on an SW20 with medium sized turbo or larger I would just go with the large cheap water to air cores everyone seems to be using positioned on the side of the engine bay where the air filter is. Super short IC piping and out of the way heat wise. You keep your boot intact and can fit a dedicated fan to cool the engine bay where the intercooler once was.
One last thing I would say is, I thought a TD06 running on a stock motor (with ecu) wouldn't get much higher then say 220-230RWKW anyway. DVSTR8 on here has a TD06 on his gen2 and I think it is around 210RWKW.
Maybe people are getting more these days? I haven't been following this sort of thing for like 5 years now so out of date haha