Chad, I'm not a Subaru expert but I'd just be really surprised if you needed enough oil cooler for 1500HP to keep your temps down. Just doesn't make sense. I feel something else has to be going on. I'd look into what Jeff said about the timing.... call your tuner, give him the logs and ask him if he sees anything in there that might contribute to such high temps.
One suggestion I have to add an inline oil temp sensor to your line from the sump to the engine. You can get them here:
http://www.racerpartswholesale.com/p...ab_Oil_Coolers They basically allow you to keep all your existing AN hoses and fittings and it just goes between two of your existing AN fittings; provides you with a 1/8" NPT female socket that you can then put an oil temp gauge into. If the temps coming from the oil tank and going to the engine look good, then you know the issue isn't your coolers or your tank heat soaking. This would be valuable data.
Like the other's, I'd be sad to see you go as well. You've come a long way with the car and it seems you are only
one issue away from fully dialed in.