So I just replaced the head gasket on my 95 Honda Civic. I was told it could be on backwards/upside down. The car will start right up when the engine is cold. But once it's warmed up, in order to start it again, I have to remove the radiator cap. If I don't, the hoses, both the front and the lower bypass hose in the back of the block builds up pressure. Also, while running, if I press the gas to hard, it trys bogging down, or a loss of power. There's a lot of blow back when I take the oil cap off the top of the engine. But the engine isn't overheating from what the temp gauge is showing me. Before I replaced the head gasket, it would read that it was overheating. I also replaced the thermostat. It was also mentioned my timing was off but I didn't mess with the timing at all. Just marked the belt location and slipped it off the very top gear located next to the valve cover. Could the ignition timing be off?

 

whoever replaced needs to take a look at it.

 

What engine block and head are you running? Here's a pic of the B7 with the head gasket upside down.
The head bolt holes on the ends near the intake wont line up, so it should have been really obvious if it was wrong.
Hows your exhaust system looking? A plugged up cat or a very restricted muffler can cause some of the issues you are describing.