Well the things are much better now as me and my father corrected the pipes (took some help from the above picture as well) and tried to set the race by ourselves because I don't understand why no mechanic has proper experience of this vehicle, so far we have tried 3 mechanics and none have good experience of mini, they all try to test on it.
Now the race is much better, but there is an annoying problem we are facing since we purchased this vehicle, I think you as a mini owner will understand this. The problem is when we start it, the race stays on 1000, which is pretty good (The water is also coming from silencer means it is well tuned and engine is in good shape). We turn on AC, head lights and put it in gear and the race stays on 1000 rpm/s or a little less like 950 due to load but as soon as the temperature reaches half way in meter during driving the race begins to drop considerably (like it comes on 500 or 400) which causes the engine to switch off, then we have to start it again but the race stays on 500 - 600 until temperature goes down then it becomes normal.
I have added your thread in my favourities, I am going to ask any further questions on your thread as it appears to be a very active thread with so many users. I'll also send you an SMS tommorow as its late at night right now.
Take care and thanks for the help.