I have the JB4 and love it. The way it changes how the car drives is awesome and i also drive my car every day so driveability is not an issue.
In regards to the hard first to second shift, all 6mt 335's do that until you delete the clutch delay valve. Search CDV, CDV delete, CDV mod, or clutch delay valve and you'll understand what i'm talking about.
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E90 335i xDrive 6spd, Nav, Prem, Cold Weather, & Sports package - Msport Conversion
FBO + Meth JB4 ISO, BB flash, VRSF DP/FMIC, ER CP, Stett, AA Exhaust & more
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/// Shop I use: Aci Dynamix 408AWHP/ 483AWTQ Uncorrected Mustang Dyno