Rattling or ticking noise

Okay so I have a custom edition and I had an issue with the car about a month ago when I bought it. It would just quit running while driving down the road and sometimes would not restart for up to a hour maybe longer a few times. Well, I checked it all out after breaking down and found that I had a plug wire that was burnt up. The little tail inside the wire was completely burnt out. My plug was still firing just burning my wires up. So that issue I can solve. However, I have been hearing this rattling or possibly a ticking noise coming from the underneath of the car while I am accelerating. It makes the noise each time I give the car throttle and once its running at a steady speed, usually sixty mph, there is no noise, engine runs good and is quite but as soon as I break and give into the pedal again comes the noise. I am wondering if a transmission leak I have discovered could be the cause of this noise. I am concerned with the transmission because it does have a leak and also at times it will shift a bit too hard. So could this troublesome noise be caused from my transmission or maybe even the manifold rattling around? Please any help or ideas would be greatly appreciated.