1988 Other Mitsubishi Models Engine dies when put in drive o

1988 Mitsubishi Mighty Max Truck 2.6L, 4x4, Auto, Carb

I bought this truck in this condition.

The engine dies when put in drive. It does not do it
when the engine is cold.

The previous owner went around the neutral switch
so a person could start and take-off while in gear.

Once on the highway the truck runs o.K. However
Whenever you slow down the engine will die unless
you put the gearshift in L2. And if you slow further
down you have to go to L1 or the engine will die.

The truck is a little weak while driving. Sometimes
when the truck is in neutral the engine will die
for no apparent reason.

The engine was supposed to be rebuilt a while back
The oil pressure is good.

There is no air filter or housing.

The Ignition timing is o.K. I also changed the
ignition coil
I pulled the spark plugs out. 2 plugs had black soot
on them. 2plugs were o.K. (Brownish white)

Does anyone have any suggestions?