if you have a minute....

i have a 96 tacoma-
this is the first tacoma i have owned (4runner and landcruiser, but no tacoma) i have had it for almost two years with no problems (had to have the cat replaced right 6 months after i bought it). recently its had a funny smell like its running "rich", but has run fine. until this morning. i drove it to the gym-no problems. i got in it to go to work- problem.

it was hard to start- never does this.
idle is low for a minute then evens out- and idles fine.
however when you give it gas it bogs (for lack of a better word) way down and almost dies. i only drove it a few blocks before i decided to return home and get the 4runner until there was more time to check it out-

my less than educated guess is i MIGHT have a spark plug fouling out- the only thing that concerns me is i have a puff of smoke coming the left side of the motor by the exhaust manifold. this smoke only appears immediatly after letting off the accelerator.

my question is: could an exhaust leak cause the type of problems im experiencing? or is this a spark plug?

pardon my ignorrance on matters w/ this vehicle (everything else ive owned has been old pre-1987)

thanks in advance for the help- J

i just received a phone call- it seems i have most likely bought some bad gas- my cousin and some others(including me)reportedly bought gas from the same walmart. they have had several calls about the bad gas and the same problems im having...