trans sport stalling, surging

hey any help is great but i am looking for toivo. any way, 1991 van 3.1v-6 stalls, bucks, intermittenly. I have changed fuel&air filter, tps, o2, plugs, wires, cap, rotor, egr valve, exhaust system. vehicle runs fine randomly, but also runs poorly and stalls unless throttle is opened above 2000 rpm....randomly. as the replacements imply, i'm mechanically inclined, but at a loss when it comes to chevy

FIrst think that came to my mind was TPS...but you took care of it...so...xcept for a freak cause, only next thing that comes to my mind is about checking for any vacuum leak..to power brake...etc...intake gasket....

I believe iirc that this is the TBI 3.1 with Cast Iron heads... Not sure what exactly is going on, But am wondering about the possibility of the Module in the distributor being bad... Seems you have replaced everything else... also suspect the MAP sensor...

Have you had the Van scaned for codes? And has the SES Light been on?