ORIGINAL: blhollo2
does the pinch test work on gas engines as well?
It should do - I've used a similar principle tuning up & balancing carbs on old (old 1960's british cars). With pretty much any combustion engine if it's running rich and you reduce the fuel flow you'll get a brief increase in RPM. The same works the other way - if it's lean and you reduce the airflow you'll get the same increase.