This article was taken from thirdgen.org
After doing this myself on my engine (88' 350 TPI) I noticed a difference in the throttle responce right away, as far as horsepower, well I've heard you may get 5 additional HP out of this.
From what I have read GM incorperated this into the throttle body to prevent any kind of freezing of the TB valve in extreme cold conditions by having water from the cooling system run through it.
This heats up the throttle body quite a bit (just try touching the "Tuned Port Injection" plate after a long drive) and from what I understand there is a possibility that the incoming air may be warmed slightly.
You want the air going into your intake system as cool as possible I've heard, cooler air has more density, that's all I know.
There are two ways to do this, both have the same results, I will cover both in this article and you can decide which is to your liking.
The above diagram shows the "quick" method using a hard tube (approx. 58") to connect the existing hoses using clamps.
This takes little time to do, however if you are a stickler for details as I am this looks like a quicky job.
I simply got a new piece of 5/8" hose with a built in (90 degree) elbow, and ran it from the black plastic heater control valve/diverter and down to the intake manifold outlet this took about 10" of hose to do and looks much better!
NOTE: Place the elbow end of the new hose at the intake outlet.
Now after you have everything back togther take you car out for nice long drive and when you get back, open the hood and feel the TB, it's cool to the touch!
You can leave the water outlets on the TB open if you wish, or do what I did!
I got some new 5/8" hose and from the left side TB water outlet ran the hose over past the battery through the fender and down under the battery tray , attacthed a small pickup funnel to the end of the hose and mounted it to the fender support bracket facing forward for maximum air pick up.
Then another piece of 58" hose from the right side TB water outlet ran next to the upper radiator hose, down next to the radiator and under the car, pointing rearward.
What this does basically is "air cools" the TB housing while your driving, I don't have the air volume specs if there is any to take in the first place, it's just an idea I had and I decided to try it.
Remember I cannot prove if this really has any effect at all it's really just a little experiment of mine so if you choose feel free to try it!
ATGO is not responsible for any damage done to your vehicle by following the above instructions.