Modifiying the standard Nissan (JECS) ECU is a very popular tuning method due to the relatively low initial setup costs.
Chiptorque - notice switch near LED to toggle between the Tuned and Standard maps
AP Engineering - Apexi Power FC
Apexi PowerFC RNN14
Custom Job
RS Yamamoto
JUN - http://www.junauto.co.jp/products/electric-parts/ecu/?en
Bad Biki Daughter Board
No description
Tomei (Modified Factory)
PowerChip Daughter Board
PowerChip Daughterboard
JAM Sport Daughter Board
Mines
Central 20 ECU
PowerSource Selection
SARD ECU
Red Zone
Tomei ECU