problems after replacing bypass valve

[JarlSX]

hi,

r53 Cooper S owner from the Netherlands here, desperately looking for help

i had the famous stutter, so i replaced the bypass valve on my car (after first replacing the spark plugs), using this howto and now have a huge problem

i did the ecu reset as described in the howto, car started normally and all seemed fine, went for a test drive, took it slow at first and was drive fine, until i punched it so the supercharger would kick in and lost all power

engine check and EML lights came on and engine was running on 3 cylinders
i pulled over, switched off the engine, started again and it was fine again, but within half a mile it did the same. restarted again, EML light disappeared, engine check light still on, and i drove home slowly (with all 4 cylinders firing

had the computer read by a garage, 1 error code pointing to the throttle body, so i went home and took it apart to see if i had missed something
couldnt find anything tho, put it all back together and its still the same thing

it drives normal unless i punch the gas, EML and engine check come on

my questions:
firing on 3 cylinders, is that normal for 'limp mode'?
do i need to have the computer reset by BMW after installing a new bypass valve?
or could this be the throttle body itself?

i really hope someone can help me, i could drop it off at the bmw dealer but am afraid i wont be able to afford them

thanks in advance!