We took the car to a dealer to have its first service performed. when we picked the car up the service advisor reported that they took the opportunity to "update" the transmission software which I was not asked or advised of prior. I asked what changes I would notice and was advised "none" it was a slight change in the software package that the end user would not notice. We drove the car home 330km and did not notice anything different about the car or shifting however the drive was at highway speed and we did not stop or make any large speed changes. During the next few weeks my wife used the car to travel to work. We were going into town about three weeks after the service and it was the first time I was driving the car since. I pulled in to a merge lane where I needed to accelerate from about 20 km/h to 80 km/h in a short merge lane to blend with passing traffic. as I straightened from the curve I applied throttle to accelerate and found myself pushing the throttle further than anticipated but no reaction from the engine so I kept increasing the throttle position as I was running out of merge lane and traffic was approaching from the rear. I now felt that I was down considerably on the throttle and trying to decide if I should abort when suddenly the engine came to life and the car accelerated very hard which input harsh steering changes as the front tires threatened to loose traction. I began releasing the throttle to gain control while the approaching traffic was breaking trying to understand what I was doing. This event has repeated time after time and can be replicated at any time. My wife said she noticed the same but thought she was doing something wrong. When this happens it can take your breath away and I would consider some of the events as close calls. I have contacted the dealer that installed the software and asked them to remove it which they said they were unable. I have complained to another dealer and asked that they remove the software and they have declined however they did confirm they have had several complaints after the software update. We have been dealing with this issue for the entire ownership of this vehicle and have made driving adjustments to allow sufficient merge distance however as I drive the car rarely I sometimes forget and find myself in close call situations. Solution, NEVER let anyone connect to YOUR ECMs without disclosing the entire bulletin and you are comfortable with all the changes.