Question on Grand Am 99 Quad 4, 2.3 liter 114k on it.

[Justaboi1981]

Ok heres the problem. In the last year may car has had some problems. Its the same one over and over again and yet it con'ts to get worse and worse. I've taken it in a whole bunch of times. Let me tell what its been doing and what its doing now. In the last year my Miles Per Gallon has dropped. 22 on average i what i have seen in the last year. with 25 on the highway. When i start the car up cold in the morning there a hestatation on the car and when i push the gas down it doesn't move very fast or well. It rides very very rough. Usally it would just come out of it after giving it a little more gas a 30 seconds. Recently it has been very cold here and it has gotten worse. No longer does it take 30 seconds to come out of the problem now its taking 2-3 mins or riding rough. When it starts to right really rough the TRAC OFF light comes on. On a few rare times its taken longer and the Check Engine soon light comes on. Usally the light will off by the end of the day. But even more recently it has started to misfire while driving. Usally around 2k rpm up near 70 mph. It will start to miss out on going up a hill. And last night it was the wrost i've seen it yet it started to while driving the rpm kept going up and down like it was having the same problem yet while the car was warmed up. Werid i know. I've had the boots, boot wires, spark plugs, a full tune up done on it. Nothing seems to help. Someone at the dealership said it might be a headgasket leaking into the one of the cinyldners causing it mis fire and cause of the cold weather its causing the metel to contract and the crack get a little bigger? Does anyone have any ideas for me?