Here's some info, that I hope will be generally useful.
The water routing on FI third-gens serves multiple purposes.
On TBI's there's an outlet, at the rear of the intake manifold,
that goes into the control valve, which routes it through the
heater core, then back to the radiator, or directly to the radiator.
This circulation pattern improves coolant flow through the back
of the engine/cylinder heads, one of GM's better ideas.
On TPI's the outlet is near the front, by the throttle body, so
I'm not sure of the internal manifold flow. But from the manifold,
routing through the control valve is identical.
In both instances, intake manifold heating occurs, and changing this
routing can have unintended consequences for the ECM control functions.
Carburated manifold heating is usually done with exhaust gas, so routing
of heater hose flow is less critical. Get it from any outlet, into the
heater, and back into flow towards the radiator. A control valve is optional,
and a simple 2 connection "on/off" is sufficient, as opposed to the 3
connection routing function & t-pipe for FI configs.
Clear as muddy water???