idle surge&taking off hesitation on 92-2.6
 

hello to all
my 92 2.6 all of the sudden hesitated until i reach 1500rpms
and at idle the engines idle becomes irratic like a surge
i put 104 octance boost in the gas tank plus new fuel filter
and now i notice the smell coming out of the exhaust is like a foul
smell. but still have the problem.but it does seem gas related
any advice.?? thanks jose