sambar stumbles at a point in acceleration

[TriCountyRe]

I have a 1991 ks4 carbureated trk.,it runs pretty good but when going thru the gears it will stmble at a given point of throttle. Once you get past that point with the gas pedal it carrys on ok. This trk idles fine and will not produce this siitng stll and revving the eng. I saw a post earlier about the air intake system , that might be part of my problem I didn't know they sourced thier air from the hollow frame somewhere. Please post if you can help.Thanks in advance .

[Timetripper]

A couple of things come to mind:

1. Route [as per request]: Both N/A & S/C get the air for the engine from the front of the truck.

Ducting as follows:

Manifold ---->>> Rubber Coupling ----->>> Air Box ----->>>>> Rubber Coupling
------->>>> Frame Rail [all the way to front of truck LH side]
----->>> Rubber Coupling ----->>> Plastic Duct [runs up behind front bumper]

On mine the rubber coupling that connect's to the frame rail up front was off and collapsing blocking the air at higher speeds.

2. Could be a distributor issue with timing - check that centrifical advance weights are free and not binding
Check vacuum advance diaphram is ok and hose going to it not cracked
It's worth replacing if unsure - cheap fix