Hi Terminator X5.
Thank you for your suggestion, the problem is that I do not know if my mechanic did duly follow BMW workshop manual...
I did attend previous work like injectors and solenoids replacement, but I had to take day off to do so, now I'm at work waiting for any finding from his side...
about the MAF, I did inspect it myself... first thing I did and the second thing I removed the main Air intake throttle to check if it was not dirty or blocked... clean and functionnal ((forgot to mention it before sorry)

To come back to the BMW manual, the procedure to follow to remove cylinder head and upper timing cover gaskets is simple but shall be followed, especially when we talk about bolting screws in a specific order with a specific torq wrench. He gave him those instructions, is he going to follow them... still I'm not behind his back to check! and I'm really worry about he is going to tell me after his todays investigation.

what do you think about coolant leaking option? impossible?

thank you again
Cheers