1994 chevy silverado 4.3 6cyl idles rough and surges when hitting the gas

Could be the Idle air valve. They get gummed up on ALL vehicles and cause idling and stalling issues. especially when cold.

Check the vacuum hoses for a leak.

2006 Chevy Impala LS 3.5L Surge Under Load - YouTube

? 3:09
www.youtube.com/watch?v=sD-swFhMORM
Jan 22, 2013 - Uploaded by Gary Castle, Jr
Surge while driving. ... 2006 Chevy Impala LS 3.5L Surge Under Load ... How To Fix Or Prevent Stalling, Surging Or Rough Idle, Cleaning ...

engine idle then take a screwdriver and hit lightly the MAF sensor if engine stall then maf is defect.

check throttle body and check for codes

battery,or altenator

ENGINE SURGING COULD BE WEAK FUEL PUMP, STOPPED UP FUEL FILTER,BAD TORQUE CONVERTER SOLENOID OR TORQUE CONVERTER. OR FAULTY TPS.

there is a lot of reasons to make it idles rough .
and you have to diagnose by it by diagnostic tool (scanner)

i think if you checked the sparking plugs and map sensors then check your distributer its maybe not delivering the current nedded to perform the spark to some of the cylinders

If your idle is going from 500rpms to 1000rpm's fluctuating at and idle your EGR valve is probably carbon up and needs cleaned or replace.

may be the egr valve