Then it's running well rich, the breathing has been modified, or the breathing system is clogged up. At least in an RST
If the fuelling system is based on an air-flow meter or is an alpha numerical system then you are just basicly creating an air leak and the engine goes lean, and stalls.
If the system is based on a MAP-sensor, then the air leak just increases the idle revs.
A whole different story is the lambda correction which tries to compensate for the extra air.
The FRST has all these systems, so basicly it's hard to predict what it will do. Depends on too many things.