The ISC is supposed to supply equal amounts of air to the TB's, but the firing order of a V-twin may be sucking the plunger over to the front cylinder orifice under closed throttle, or the ISC may stick due to oil build up inside it.
The spec for idle rpm is 1200 to 1400 rpm.
What if the engine won't smooth out below 1400 RPM?
If the ISC is working correctly and regulating air flow equally to make the engine idle at the preset RPM of 1300 rpm and the mechanic opens the air screws to make the engine idle faster, the ISC should react to reduce air flow and slow the idle RPM down.
If the TB's were really misadjusted by some overly enthusiastic mechanic or the air screws are dirty or the ISC is clogged up with oil from the crankcase breather system or the TPS is erratic, the home mechanic won't be able to easily synch the TB's.
The lurchiness when rolling off the throttle which made me believe that my TB's needed synchronizing was actually caused by the ISC and the TPS.
I researched the TPS problem and found that Suzuki changed the part number.
So I googled the new part number and found some discusssion on other forums.
Some Vstrom riders were talking about the erratic TPS sensor on their machines causing stalling.
They said that the TPS was sensitive to heat but that the change in voltage wasn't high enough to cause the ECU to display a fault code.