Originally Posted by neovb
So, I pulled this out of another post on here (330d tuning options). This chip-tuning option is out of the UK, but apparently controls both fuel and boost (unlike JBD, which just does fuel). Looks to be semi-programmable too.
I checked out the site, and guess what? They have an option for the US-spec 335d. The module costs about $420 USD, with shipping included.
A forum member did a dyno comparison of the VAC (fuel and boost) vs. the JBD. Results were VAC made a little more torque but JBD a little more power. Very close though on both. Here is the dyno chart he posted. The problem with these fuel and boost units is they can't actually change boost without also intercepting the MAF, waste gate, MAP, and boost solenoid (4 additional plugs). Tthey only intercept the MAP (1 additonal plug), which allows you to read boost but not change it. The early JBD actually controlled boost as well with the 4 extra plugs but they found boost was already so high there was not much additional gains with more, so they streamlined it to the simpler and easier to install product we have today in the JBD.