Yes, it is already installed (check out the link for the exact tank I used); the battery is now in the trunk.

Yes, hot water returns to the tank. The configuration I have is: Tank --> H.E. --> pump --> intercooler core --> back to tank. I think some people are sending the hot water through the H.E. to be cooled before returning to the tank. They pull the already cooled water from the tank and route it directly to the intercooler core like this: Tank --> pump --> intercooler core --> H.E. --> back to tank. I'm not sure which works better or if it makes a difference, but I may try doing it this way if others find it works better.

It's hard to tell exactly how much it helps for peak IAT's since the last time I logged (before the mod) was in 90*F weather. After the tank mod I checked, but the outside air temps were in the 60's and 70's. It definitely cools off MUCH quicker. The intercooler core is not getting as heat soaked now. The IAT's still spike to around 150*F under hard acceleration, but then immediately drop down around 100* or less within about 15 seconds after letting off of the throttle. They usually hang about 30* over ambient during normal driving. I really believe the IAT's are still spiking due to my intercooler being coated with oil from the PCV system. There is oil all over the inside of the intake tract (and now water due to my leaky intake core). The new Code3/Spearco intercooler core should take care of both of these issues. Hopefully then, I won't see the temperature spikes under hard acceleration.

*Also note that I originally installed the tank using the Bosch pump. I haven't checked the IAT's in the week or so that I've had the Meziere pump installed.*