Water Pump/Radiator Questions

I converted the front drum brakes to power disc and after completion noticed that I was overheating. I did a lot of adjusting, etc to the brakes to make sure they weren't dragging and I feel pretty good it's not due to the brakes because I can overheat literally running the engine for five minutes and driving around the block a few times. Next I flushed the system completely with water and then refilled with the Peak Coolant. I don't think I burped the system properly though so I had to go through the process of trying to burp it. Still overheating, so I changed the thermostat and refilled with Peak. Still overheating so I drained about two quarts and then refilled with water and water wetter. I live in Florida so it seems like I should have more water...according to what I read on here. The water wetter helped a little, but still the engine overheated on a grocery run. The real problem seems to occur when I'm sitting at red lights. I did convert from single exhaust to dual exhaust (turbo mufflers) due to a rotted out exhaust y pipe. I don't know if somehow that could be causing the engine to idle to fast...which I've read in my manual is another possible cause of overheating. At this point, once I change the water pump I'm thinking I'll take it to someone next to see if they can diagnose the issue.