Camaro engine flush – which one is heater inlet hose?

96 5sp 3.8 117k

Diy flush kit says to install the tee on “heater inlet hose”, NOT on the hose “from firewall to water pump”.
On my other, 95 3.4 camaro, mechanic pointed out the right one and it worked great, flushed the junk out, had nice green antifr in it until it got totalled…:(.
On my 3.8, the 2 hose outlets on the engine block actually have arrows on them. One points into the engine and one out. Mech said that the one pointing away is the heater inlet hose. It actually had a piece of pipe spliced with clamps into it from a previous owner.
Installed tee, flushed junk, but not as much as last time. Also this time thoroughly flushed overflow reservoir (didn’t do on last one). Now, while the antifreeze in the rad is almost as green as when I put it in, the cap had brown slime on bottom. The reservoir, though, despite having been flushed, must be full of the brown slime, as the dipstick comes out covered with it (up to appropriate level that is).

So I’m wondering. Did I install the tee on the wrong hose resulting in incomplete flush (it’s done with engine running and a running hose hooked to it till clean water comes from top of rad)?

Or did I install it on the right one and it just for some reason got this dirty this soon (month or so).
What reason would it be? Is my rad rusty? Should I flush again?
Thanks

It sounds like you T'd the right hose, does it go into the firewall?.. Did you use a rad flush solvent?? water alone wont remove a lot of the sludge and rust build up, you could have just loosened ut.. Did you have your heater on full? Try flushing it again and see if it clears up

used solvent for specified # of hours, heater full blast...can't see where hoses are going...thanx