I have the 04 GT with the 3400 motor. After taking a trip to Minnesota and pulling a small trailer back with a kids go cart, small mini bike and some other random things it's not running right.
I got in the car a few days after to go to work and noticed that the car wouldn't accelerate without hesitating and didn't seem to get full throttle. Wasn't OH and performed almost normal. I parked the car and didn't drive it after that. After almost a year I decided to try it again and got it running and the car idles fine but as I'm driving it, it seem to be a bunch worse. I have to baby it to get acceleration and noticed that it started to heat up faster than normal and had to turn on the heat to cool it down. After stopping I checked on the water to make sure it wasn't low and noticed what looks like oil in the water. The engine isn't throwing any codes and the oil looks fine. So the big question is what's going on? Is it a head gasket problem?

I did replace the upper and lower intake gaskets and we made two trips before all of this to MN with no issues. Could the intake gaskets cause all these issues? It would seem to me a bad HG. I will have to get a compression test gauge and see what'
Up. I don'the see how I can do the hydrocarbon test with the water looking like this. When I first looked in the tank it looked like some oil was in the water but Ive let it sit and when I checked it again this is what I found.

 

Also I didn' use thread locker on the lower IB because the instructions I used didn't call for it. Imy guessing the blots have loosened up.

 

SOLVED--It was a clogged cat. I cut it off and replaced it with a straight pipe. Runs like a champ.