The Fidanza fly comes with two fitment options.
On the end of the crank there is a small dowell pin.
On the inside of the Fidanza fly there are two small holes.
One hole is marked front and the other is marked rear.
What this means is that front wheel drive cars like Maxima or Altima the dowell pin locates to the hole marked front and the rear wheel drive cars like 350Z, G35, G37 the dowell pin locates to the hole marked rear.
Get this wrong and the car will not start as the timing will be "out".
If this is the case then the only remedy is to pull the box and fit the fly properly.
I have no 1st hand knowledge of the American F1 fly that you fitted but I would assume that there would be similar fitment options.
Hope this helps.
Alex.