Well yesterday on my way home I was at a stop light and when the light turned green I accelerated pretty hard I was at about 4.5-5K in first when I noticed a sharp decrease in power ( it still accelerated just not with as much power) I look back right when I feel the power drop and notice some black smoke that had come out of my exhaust

I then push my clutch in and start to shift normal but notice that the car is not making as much power as it was before my puff of black smoke. I get in today and everything seems fine but the power just doesn't seem there it might be all in my head but it doesn't seem as powerful as it was, but it does have more power then yesterday after my little incident happened.
Does anyone know what might have happened ? any suggestions ?? I don't know very much about engines but I might be leaning towards any of these things: bad spark plug or bad gasket or maybe a lost cylinder

I'm not sure I just don't have much money to spend right now...I hope by driving it around as little as I can until I am sure what happened I don't hurt my car anymore, but money is kinda tight right now.
I know I should take it to Ford since I have an extended warranty on my car up to 100K (i'm at 33K now) but I can't afford to take it to ford then they say that it was something wrong with the exhaust or y-pipe or any other mods that I had put on that might have caused this since they will charge an arm and a leg.
I know this sounds rediculous but I actually hope that if something is wrong, that it is in the engine so ford will definetly cover it with only $50 out of my pocket. I know that if it is in the engine they will cover it since I haven't added anything to the engine except for a K&N Filter. Well below is a list of all my mods so any help would be appreciated
Thanks,
Louis