Ya, that crazy steve's intercooler does take up a lot of space in front of the radiator.

So, I figured out the knock (very little baby grumble) is only at idle. It runs great throught the band.

 

If you're running the heater on full hot it is removing heat from the cooling system (which is a trick you can do if a car starts overheating or has a subpar cooling system and you're tracking the car and temps are rising). If it truly is running hotter when cold I'd bet you'll find the answer in the powertrain control module's calibration and it has altered the fan engagement points to either keep the engine hotter so you do have that heat and/or for better emissions in the colder weather.

 

...or the fact that the heater core return hose is dumping in cooler coolant keeping the T-stat closed longer.