In the other HTBI thread I mention the "other" sensors that often don't come with the kits.
The reason...the ecu looks for all inputs, VSS is obvious because it tells the ecu that the readings from the MAP sensor and the TPS are "real", but also it leans the mixture upon slowing down. The brake switch leans it faster.

They included these inputs so that drivability are the best.
When you exclude them, those areas suffer with odd problems.

VSS and brake switch inputs are huge for best performance, will they run OK without, of course, just know why they do funny things.

SD