VAC Motorsports Intelligent Diesel Control Module for all Diesel Powered BMW Cars

Once the product was installed I did notice some performance improvement initially but it seems to have backed off a bit. I'll pull it out again to see if it's just my imagination. Cons: There are no instructions provided with the module. If I didn't know where the specific connectors were I would have had to spend some time online. There is no provision for mounting the module. I was left to fashion my own. The main pigtail is way too long. It is also very difficult to get all of the wiring and connectors to fit under the engine cover without applying pressure to the connectors. Good product but a rather weak execution.

I just installed the diesel control module over the weekend and from my first drives, it seems noticeably more responsive across the power band. I'm pleased with my purchase so far. I'll update my review after driving it more over the next few weeks.

It provided a very noticeable increase in power across the entire rpm range. I swapped between this one and the JBD and preferred the VAC one b/c it never threw any codes or caused any reduced power situations (the JBD did). It also seemed to produce slightly more power below 2000 rpm. Very happy with my VAC module

First and foremost, the 3.0L Diesel is a terrific engine to start with. I thought the gas I6's and turbo V8's were great, but I think this is the best balance of all that I have owned or tried. The torque and economy of this engine really makes me wonder why there still are very few advanced diesel engines in the USA for passenger cars.

I have used one of these on my 2010 x5 35d for about 2 1/2 years now and have been quite pleased.
Installation is extremely easy. The most difficult part is removing the plastic BMW cover over the engine. If you can use a tiny standard head screwdriver to hold in or dislodge a retaining clip that holds the OEM harness to the fuel rail sensor and then plug this in, you can install it.
I was worried at first because I would receive some random Engine Exhaust Level warning lights, but I have since had the recall work BMW issued for nearly all 35d engine models performed that involved an ECU flash and the issue has never re-appeared. So it was a factory issue and not a result of the unit.

Fuel economy has been consistent (maybe even a little bit better) than what I was getting before it was installed. To me, 30.7 mpg on the highway and 24 mpg in the city for a 5,700 pound SUV that hauls @$$ if you should decide to stomp on the accelerator is quite good in my book. Power delivery is just as smooth as when the vehicle was stock. I have owned a Audi 200 Quattro in the past that I had the ECU flashed and turbo waste gate spring replaced. It went from a respectable performing sedan to a fast but 'Peaky' sedan that really wasn't that much fun to drive in town anymore. This is not the case with this upgrade as it has the same driving characteristics as before, but with just a little more spunk once you are up and going and those turbos can work their torque producing magic.

Review:
PROS: Nice power boost and slight increase in fuel economy!
CONS: I experience harsh downshifting from 5 mph to 0 mph when attempting to ease into a stoplight or when caught in bumper-to-bumper traffic?

*VAC Tech feedback*
We have never heard of this downshift issue before and have never been able to replicate this in testing. We recommend checking your transmission fluid level.

I have grown to apprciate several BMW on my life, but my 335d is now my favorite. The VAC module is by far the best upgrade I could have wanted. It hasn't caused any issues and performed better than the ECU flash I ordered from Europe.
Now I have no warranty issues as well.

A side effect I have found is improved milage by about 2 MPG and I don't drive slow. Thanks for a great product!

4 stars because when I bought it, it was $650 and now when on sale its $499. Wish I had asked.

In terms of wheel hp the base peak was 225 hp @ 4K (~260 hp) and jumped to nearly 260 hp at the same rpm. (~300 hp crank) on the dyno. (plus 40WHP)...

...I'm pretty damn impressed with the gains. As you all know, in stock form the car is deceptively fast. Basically once you spool up the turbos, the thrust is linear and drops off at higher rpm as we have come to appreciate.

Now, once the turbos spool up, the car goes like a bat out of hell and it doesn't give up at higher rpm's either. The thrust is still linear but man does it push you back in your seat!

With this easy mod, the car is comparably E46M3 fast! You still have a bit of lag for the 0-60 sprint but it's still faster than before. At all other speeds, the car is a beast.

I have not noticed any decrease in MPG but I need to be probably do a before and after comparison since I can unplug the module at will.