91 mustang lx. i got some real problems here.

driving along when suddenly, the horse power goes away. engine runs but real rough, when in gear you can put the pedal to the floor, but your taking off at a crawl. cant get any faster then 35 in this condition, plus theres the strong smell of gas. and yes, now shes drinking gas.
to add to my confusion, this problem comes and goes. sometimes its quick some times its over hours. ive tryed to see if its something that triggers this behavior, but so far its seemingly random.
while checking the radiator and filling it with anti-freeze, some gunk floated to the top. it has the consistancy of hot fudge, but is far from edible.
based on this information, anyone ever have anything like that happen to them? what if anything could it be.