firstly a lot of very uninformed people on this thread ...
i had a 135i and a 335i (for those that did not know) ... someone made a comment that it could have been a 125i and not a 135i, and this is very valid. A 125i with an msport kit looks very similar to a 135i and if you don't know the subtle differences you will never know. Those differences include a blacked out dual exhaust pipe, the 135i does not have any fog lights, and the calipers have the BMW lettering on them! ... its subtle esp the fog lights, i did not pick this one up until i owned one ...
The 135i does not have a sport button or launch control with either manual or auto transmissions. With the altitude in GP the car is extremely quick, quicker than an RS4, SLK55, DCT M3 through the gears (eg, rolling second etc) except rolling 1st, quicker than an Z4 Mcoupe. Whats interesting the hiding the 135i gave to an SLK55 up here was the same hiding the 135i got from the SLK55 in Cape Town

... both the same cars used in both runs ...
Against now the ST, if anyone want to tell me that a stock ST is quicker is talking an entire load of bull****! ... and i will put R50k down to prove that a stock ST vs stock 135i, the 135i will not just beat put totally annihilate the ST ... any takers ... ? I ran one with my pig weighted 335i convertible and it was not even a contest to start off with ... BUT any car given the money and time can be made to do some serious times ... if that ST is running 234km/h on a km stretch, it is insanely quick. My E46 M3 at the time could manage only a 200, 996 turbo Porsche 230km/h odd ... heck my current RS according to car Mag does 240km/h on a km ... so in the end its just unfair to compare a modded car to stock, simply because its a case of "how long is a piece of string", the possibilities are very high in terms of "how fast" when it comes to modding.
Then someone said the 135i is not a race car when compared to an ST ... you joking right? The next time you standing next to a 135i, have a look at those brake calipers ... its just BMW's way of saying this car is about performance. Many other components on the car are geared towards performance... do a bit of research on the web and you will see this ... many have commented that the car could have gotten the ///M naming ....
give me a track, and give me a straight line and ill show you just how bad a hiding the ST will catch from a 135i ... but its unfair to compare the two cars, one is a single turbo 2.5L motor versus a 3.0 twin turbo (or biturbo)
heck given the time and money someone can mod their UNO turbo to kill my RS

... and ive seen some very quick UNO's so i dont doubt that
In the end if someone wanted to swap their 135i for an ST, the ST owner would not hesitate for a second, cause he knows its the better car and him denying this, just means he is "jelas!!!" ...