Ok guys. This problem has been vexing us for 2 years. My 1991 Chev 4x4 with a 350 surges if you stab the throttle a little too hard off-idle. It is like a bad timming chain, but it isn't. Changed everything we can think of from a donor throttle body 350. It doesn't feel electrical. It isn't the idle motor (2x new ones already) It isn't the timing chain. Oxy sensor? Cracked head?

Here is your chance guys. 2 years we been chasin' this thing.

You don't give out a whole lot of information about the engine. Headers, cam, lifters, lifter lash or preload, intake manifold, ignition, compression ratio, quality of fuel, initial timing, thermostat, injector size, wear on engine, gear ratio, weight of vehicle and average altitude are a few of the things that can be considered when attempting top guess what can be adjusted to make it run better.
Did I list vehicle color? OK seriously, if you have been chasing this for two years you should be able to give us some information to help us along.
I'm not sure what you mean by surging. Can you explain?
Squido

EGR valve?

You don't give out a whole lot of information about the engine. Headers, cam, lifters, lifter lash or preload, intake manifold, ignition, compression ratio, quality of fuel, initial timing, thermostat, injector size, wear on engine, gear ratio, weight of vehicle and average altitude are a few of the things that can be considered when attempting top guess what can be adjusted to make it run better.
Did I list vehicle color? OK seriously, if you have been chasing this for two years you should be able to give us some information to help us along.
I'm not sure what you mean by surging. Can you explain?
Squido
Dead stock. Maybe not surging. If you hit the throtle a little bit hard, it stumbles quite badly to the point that you think it will stall.

I have an answer. Intake manifold gasket. It was that simple. Now you guys know too.

Just a WAG, as I'm trying to learn EFI, due to a TBI swap. Could it be in your AE tables ( going lean at tip in ), or fuel pressure dropping out on you? Have you had the chance to do any datalogging? HTH, Al

The saga ends. It was not the intake gaskets. It was the damn egr valve. The valves get weak in there and they open up off idle and dump a bunch of recirc in there and the computer just can't handle it. Put in a used valve today, and it runs like, well, not new but acceptable. Got a miss at idle now to get out. Probably a bad plug or wire. Cap and rotor are sound, so that or dirty injectors.