Yes, this question has been debated over 100 years!
in every woodgas book!
No one is comming downhill from the Himalayas, anyway... so if the motor goes well with its gasifier system on idle for 15 minutes and more, there is just a little "noch" moment in the retaking of driving power, when the land is flattening out, or a new uphill is about to be "taken".
With a manual gearbox you can use the motor for pumping more gas than the idle gas need, by swiching off the ignition and giving a little foot (pedal) gas. That is called motorbraking...
Perhaps too modern vehicles also will make a mess with all kinds of shutdown-functions when they are deprived of current?!
Hope you can circumvent that!
If you reed the books, you will learn, that a hearth after heavy drafting can produce an excellent gas, because the steam boiling in the silo pushes out through the hearth, and no air is comming in with nitrogen, which normally will dilute the burnable parts of the gas by ~1:2!
If this goes too far, the motor can be suffocated by the lack of secondary oxygen (air).
This is typical with T-mixing, where the mixing ratio (air/gas) happens above the common throttle.
In this case, the high succing-vacuum is under the common (for both gases) throttle.
Above the common throttle and the succing vacuum you have the two (freely compeating) entrance routes of free flowing gas and air.
This "competition" is under normal power conditions a place with a swift flow-through, and in consequens of that, you have flow resistances in both entrance-routes.
With this flow-through, you can balance the flowresistance between the routes with the traditional hand-regulated air-flap.
That is the traditional way to set the mixing-ratio.
But, when the gasgenerator is pushing out more gas than needed, the mixing ratio is upset, as the t-mixer is dependent on setting the flow resistance equal in both arriving routes (legs).
When the gas is flowing into the T-mixer without succing, it is impossible to balance the "flowresistances" and the air/gas ratio!
This will not happen with the twin-flap dispenser, because it is setting and controlling both arriving air and gas routes' flow resistances independent of which "mood" the gasifier happens to be in!
Pushing or resisting...
The twinflap dispensing is dependent on the always
equal flow areas and equal pressure drops
over both flaps --- from cranking to modest high power levels.
At WAT level the twin flaps are no longer the dominant resistant for flow control, so the flow routes for air and gas have to be made absoutely identilcal from the sampling points for the flow routes to the dispensing flaps, and to the swirl mixer.
Sampling points for the membrane, which regulates the arriving air pressure according to the arriving gasflow pressure, when there is a definite pressure drop in the gas line.