My truck has the 5

My truck has the 5.8 dual tanks 5 speed.A few months ago the check engine light started coming on and going off at will. When its on, the truck runs rough and it will only accelerate with slight pedal pressure. When under a load or heavy pedal, it staggers and wants to fall on its face. But when the light goes out, it runs great. Well now it wanst to stay on all the time. Its also hard to start once its been setting for a while. I've replaced the fuel filter, fuel pressure regulator, both fuel pumps and the ignition switch. Also when the light is on, the fuel pumps run constantly. On a side note, a few weeks ago my temp gauge needle stays all the way past the hot mark but may jump over to where it should be while going down the road, but when the key is turned off, the needle goes to the right instead of the left like it should. Any ideas?