Radiator flushing

Anyone know of a good radiator flush? I've heard that vinegar actually works really well, but I'm not sure what to really try. I have a big 4-core radiator in Duster and on warm days, the engine gets up around 200* at times. I installed a shroud, I tried a flex fan and a MP clutch fan set, messed with different size t-stats and made sure the timing and tuning was good. The water pump is in good condition, the belt is good and I recently replaced the upper radiator hose.

I'm thinking the radiator has a clog. I used a laser thermometer while the engine was up to temp and the center of the core read 190* while the outer sections of the core read 130*. I would like to try and save this radiator by flushing it since there is no external damage to it. Even if I have to fill it up with something while sealing the inlet/outlet, what kinds of flushing agents are good? I don't know of any good radiator shops around me. Anyone have any good ideas?