Fuel control involves tricking the ECU into thinking there is more or less air traveling to the engine.  The most popular device to achieve this is the HKS VPC.  It replaces the MAS by using a HKS Super Power Flow.  Another popular device is the Apex-i AFC.  Apex has recently come out with a new Super AFC, which has more tuneablity than the old model.  The one picutured below is the old one. Most people perfer the VPC because the AFC uses specific RPM bands to do its tuning.  But the AFC does not replace the MAS unit.  A G-force ECU replacement is another option.  The downfall for the G-force unit is the fact that its not tunable.  GReddy makes the Repic III, but I'm not familiar with that unit.  Split Second has also recently came out with there ARC2 fuel computer.  This looks to be as good as a VPC with GCC combination.

G-Force ECU

Apex-i AFC

HKS VPC

GReddy Repic III