bad idle

ok so i have a 1990 b2600i and it starts up fine but after it runs a min or two the idle goes down to about 250 to 500 rpm and when i stop at a red light or stop sign it dies iv tried a lot of stuff i found one of the plugs wires arcing out on the block so i replaced them and the plugs no luck ther either im running out of ides any help would be nice thanks

is it run fine for a few mins everytime you start it up or just the first start of the day? i am thinking the choke makes it run normal, then when warm it drops down. maybe adjust the idle screw? have you timed it yet?

Just a toss but have you removed the egr valve and cleaned it up internally.These can clog up with carbon and has 3 ten mm bolts,one vac line,one electr hook up.Remove it and note the metal gasket position (this is important) and clean with a tooth brush and carb cleaner and make sure that the metal pintal(moves back and forth are free).Reinstall and see if that cleans it up.Tired so keeping it short.Unless your carb is needing cleaning and or rebuild.Try this it makes a world of difference.Under air cleaner below carb at a angle.typical b2,or b22 issue.

iv adjusted idle screw and cleaned the egr valve its fuel injected but nothing seems to help and yes it does it everytime i start up runs good a few mins then runs like crap