Steve in Seattle
No, have not solved the problem. Considering two options, keep it stock looking and buy a new 4-row, or go all the way with an aluminum replacement with electric fans. I hate to waste the money on a 4-row and not have it be enough but then do not want to modify the car to make an aluminum radiator fit.
The flow test you said you might consider may help, there are several opinions on this one. Some say the pump spins to fast and does not allow the water to stay in the block long enough to absorb the heat, and the other says it spins to slow and allows the water to stay in to long and heat up. And then there is the thermostat, 160, 180 0r 195. I believe this is a very common problem and difficult to solve. I have a 2006 Trailblazer SS as a daily driver, temp gauge stays at 210 never moves, 100 degrees or 20 degrees, uphill, downhill nothing moves it.
Let me know your results.
Tom