Alright guys and girls, I just joined this site and I was hoping you guys would be able help me out. I got 2004 dakota with the 4.7l, and after i got it I had an exhaust leak coming off the exhaust manifold, so when I fixed that I put gibson performance headers, with a gibson cat back exhaust kit. After that was done a few months later I decided to change the o2 sensors as they were going haywire. after that I started noticing slight misfires after start up when i would start driving and then they would go away and not reappear again after. I changed the spark plugs as they were bad and it seemed to go away for a while. later on it reappeared but worse, it would misfire after every start but if i let it warm up it would go away. I had codes pop up for multiple cylinder misfire and o2 sensor codes. I then decided to put in a high flow cat thinking it could be a plugged up cat causing the o2 sensor codes and causing misfires. That didn't work. so next put o2 extensions on to get rid of the code and that made it worse. I checked plug wires and they seemed fine. oh and i also brought it to a shop but they thought it could be a blown head gasket, but it shows no other symptoms of that so I don't think thats what that is. I've run out of ideas and I was wondering if anyone could help me out (sorry for making it so long lol).