I have a 2006 (feb) 2.0i 6MT X3. I had always thought I had a 2.5 until I noticed all other X3's on the road had two exhaust tips and mine only had one. I didnt even know there was a 2.0 until a month after I got the car. Keep in mind that it wasnt I who ordered the car, I was simple told the car had the small engine in it.
Anyway, on friday I was driving to my friends graduation with a girl in the front and three big guys in the back (not fat but just built). On the highway I had the pedal to the floor and the car was having trouble getting past 165 km/h.
Later that night I brought three girls back home after the graduation party, one of them was quite round. On the highway again, 5AM, clear roads, pedal to the floor, the car was now having trouble getting past 185. After hitting 160, it took a little while to get up to 185.
On my way back home at 6AM, clear roads again, alone in the car I was able to hit 210 about. Im pretty sure in the X3 manual its mentionned 198Km/h for the 2.0i max speed.
Anyway I just felt like sharing my experience with the rest of you.
By the end of the year im going to sell the X3 and buy a new 4x4 once I move to NY. I need something bigger and with twice the amount of power. The 2.0i only has 150hp