hiccup at around 40-45 mph..help!!

ive been having this problem for a while now and i just wont go away...a while ago i put 2.5" performance exhaust from the manifold back eliminating my cats.. now my 97 tahoe has this "hiccup" at around 40-45, mainly when i let of the throttle...ive chaned distrbutor, cap, rotorbutton, wires(bosh),plugs<~~bosh platinum +2.....i just put this thing on i herd about if you have performance exhaust, its callded a "o2 simulator",works great..it took my truck out of limp mode but still a hiccup at 40-45 mph...im down to...injectors, ignition coil, fuel filter,and fuel pressure check....someone throw me info please.. :confused: ....ALSO HAVE 33-12.50-15 PROCOMP MUD TERRAIN TIRES FOR SALE....95% TREAD LEFT..

ive been having this problem for a while now and i just wont go away...a while ago i put 2.5" performance exhaust from the manifold back eliminating my cats.. now my 97 tahoe has this "hiccup" at around 40-45, mainly when i let of the throttle...ive chaned distrbutor, cap, rotorbutton, wires(bosh),plugs<~~bosh platinum +2.....i just put this thing on i herd about if you have performance exhaust, its callded a "o2 simulator",works great..it took my truck out of limp mode but still a hiccup at 40-45 mph...im down to...injectors, ignition coil, fuel filter,and fuel pressure check....someone throw me info please.. :confused: ....ALSO HAVE 33-12.50-15 PROCOMP MUD TERRAIN TIRES FOR SALE....95% TREAD LEFT..

Mine was doing that. But i changed my cap and rotor,wires&plugs.
and it still did it. So i took the gap down on the plugs some more
and it went away. GOOD LUCK!!!