2006 Honda Civic A/C Cycles from Hot 2 Cold

I have an 06 Honda Civic Dx 1.8L 4-Door, i'm having a difficult time fixing my A/C problem! The A/C blows cold in the morning, in the afternoon it blows hot for a couple min and then cycles to cold air then back to hot air, at night the A/C is working perfect! I've recharged the freon with 15oz. The gauges on the robin-air machine read normal with the car on and the A/C @ max - Low Side 30 High Side 175. When I would accelerate the RPMS @ 3000 the gauges would read different Low Side 10 but would cycle back up to 30 and drop, High Side 200. I changed the Expansion Valve because the low side hose was warm, it fixed the problem! Hose is cold. The compressor engages and stays on. My problem is that its not blowing cold air during the afternoon summer heat. People have been telling me that it could be my blend door that is not closing letting cold and hot air into the vents. I also plugged the heater core hose and that made a huge difference in temperature in the A/C it was blowing cold for a while but then started cycling hot to cold once again. Hopefully theres a solution to all this!