Well as i said i have a 91 dak with the 318, and im trying to figure out why when at low throttle it feels like its chugging/bogging down... its hard to explain lol. basically when i am driving in town at the speed limit of 25mph, and im barely on the throttle to try and hold that speed, occasionally it like chugs/boggs a little until either i let off or step on the throttle a little harder. i cant seem to get it to do it at idle... any ideas guys?

 

It could be the TPS( throttle position sensor), or a IAC valve. I would check those visually and test wit a meter to see if they are good with no flaws. If nothing turns up on either of those then start checking all the other sensors that play apart in the adjustment of the air/fuel ratio. Could also be a vacuum leak. Really it could be abunch of things but have to start by rolling out what it is not.

 

91 wont have an IAC valve.... its throttle body injection.
Could be ignition related; cap rotor wires plugs
I'd be changin all that anyway if its been a while just as preventive maintenance.
91 also had a seperate inline fuel filter that anything newer than 93 does not. another "gotta replace" part if it has not recently been done. Trucks (of any age/brand) need MAINTENANCE to keep them dependable.