oh.. i've actually done this mod before.. to my long-departed old-school bimmer (1986 bmw 318i). the coolant line did not exactly go straight through the throttle body (if my memory serves me right), but it was somewhat attatched to it and ultimately and eventually routed to the heater core then back to the engine. what i did was a whole heater-core/throttle body bypass. the coolant line exited the engine, then made a 180 degree turn back into the engine bay, totally skipping the throttle body. my [newbie] theory was that in this setup, the less obstruction in the coolant line would be easier work for the belt-driven water-pump and therefore less power-loss for the engine. i took this to another level by removing the belt-driven AC as well, freeing up more power.

anywaiz, back to point, i later learned way after that colder air for the intake was better, and i thought to myself "whoa, i wonder if that throttle body/ heater bypass helped get colder air".. was just hoping to see some serious back-up here.. i now feel confident i did a good mod (even though it was in the past. haha)...

EDIT: and oh yeah, probably the important part: i DID feel a SMALL increase in power in the higher revs (above 4000 rpm). i also noticed a better/faster/smoother revving and a smoother idle. the thing is, i'm not sure which mod created this newfound characteristics, because i did both mods at the same time. nevertheless, there is NO DOUBT that they helped.