Weird Power Hesitation / loss

[91ka_240]

i have a 91 240sx KA24DE. when i started noticing the problem was around january when i put some **** gas in it for the first time. the problem is that sometimes when i start going, in first, around 2.5 - 3k rpms the car starts to kind of slow down as if ur pressing on the brake. then a second later it'll pick back up to. i have been pretty easy on my car. no check engine light. i also have a pretty bad idel to. when the car warms up it gets down to about 500 rpms then kinda goes back up to 650 then 700 then back down to 500 again. i am thinking that the IACV is probably really carbond up since its got 194k miles on the stock motor. i can't figure out the problem. so any help would be Very much appreactied.

the mods i have done to it.. MSD blaster 2 coil accel 8mm spark plug wires ingen intake and A/C removal.

[janda240sx]

Have you changed your fuel filter? or checked the MAFS, Maybe the bad gas coould have fouled one your plugs. I would check all that and clean the iacv.