Gas and Oil Home Heating Furnaces - Furnace not staying lit HELP!!!

I have a 1995 Goodman Natural gas furnace. When the thermostat is turned to heat, the glow plug ignites the four gas blowers. But after about 5-6 seconds the flames go out(the exhuast fan continues to run until the thermostat is turned down). I replaced the flame sensor, now the flames(sometimes burn for 30 seconds) the rest of the time it is 5-6 seconds. The ports on the vacuum sensor and the exhaust fan appear to be clear(by way of using a small hand turned drill bit. The drill bit stops about 1/2"-5/8" of the way in.)
Any help would be greatly appreciated Thanks.

What does the diagnostic control board tell you?

The diagnostic LED stays continues, no blinking at all.
Thanks again

Your burners could be dirty. The flame sensor has to have clean burners to sense flame properly(especially the burner behind the flame sensor). The circut board sends voltage to the flame sensor and it travels thru the flame backto the burner which completes the circut. The board senses this and allows the burners to continue to operate. If the burner or flame sensor is dirty, the board will shut the gas off to the burners in approx 5 seconds like yours is doing. If you dont feel comfortable about removing the burners and cleaning them(which is more than likely), you`ll probably have to call the pros. Good luck!

Change the board..I've run into this quite a bit with Goodman boards. Giving none or the wrong diagnostic. For some reason the board can not sense the dc micro amps created by the burner flame on the flame sensor...