The JB3 and JB4 modules are completely different; the boards are not the same. Ive had both and the JB4 is more advanced and has better maps. Power is much smoother and all the settings are better controlled with the the JB4. The Map 5 auto tune is really good on the JB4.
Also, the JB3 is no longer supported with firmware from BMS.
I highly suggest you pay the upgrade fee to go to the JB4, either G4 or G5 boards (latest version), it's that noticeable.
2011 Mineral White M3 ZCP
Stock for now
Last edited by bigdaddycane; 01-02-2013 at 09:41 AM.