96 Chevy Blazer, 4.3L V6. I have a misfire causing it to jerk and shake as i drive. It feels like it does it right as its about to shift gears, and like crazy when im on the interstate going 70+, also note it does stop as i drive during the day, its only when its been sitting for 5 or more hours and i drive it. I have replaced, plugs, wires, rotor button, cap, fuel injectors, fuel filter, and the broken vent valve on the gas tank yesterday. Im thinking surely its gotta be fuel or maybe even air intake related cause if it starts missing, step on the gas a little more and it stops untill its not accelerating at a faster pace anymore. I cleaned the MAS off with the MAS cleaner, looks brand new. I noticed i hear a little air sucking sound next to the throttle body and thought id start checking that next but also wanted to post and see what someone else thinks. Maybe even the fuel pump is just worn out cause ik without right fuel pressure it can get worn out, and the fuel pressure has had to been off for a while cause the vent valve on the tank has been broken for a while. Im not sure if I covered everything or not but let me know if you need anymore info on it.