After taking the EFI101 class, I don't think tuning on the road is a viable option. On the dyno you can map over many load conditions. In the class they had about a 10 by 10 volumetric efficiency (VE) map that was quickly tuned on the dyno. The VE map has load on one axis and RPM on the other. The dyno would hold the engine in one cell and the VE would be adjusted to get the desired air fuel ratio (AFR).

The vacuum is used to determine % load. 0 bar or full vacuum signal would be idle with no load and 1 bar or atmospheric pressure would be 100% load. A 2 or 3 bar MAP sensor would be used the same way except that peak boost would be 100% load.

The ignition is tuned after the AFR is set. It is set by starting with a small advance and then slightly increasing advance until torque stops increasing. THIS IS WHERE HP IS MADE. This is pretty much impossible without a dyno.

Suzuki throttle bodies have two butterflies. Some Yamahas has a valve on the exhaust pipe...