When i bought my Saph the owner advised me that the am valve was disconnected as it affected boost!
Done by a so called tuner!!
Been doing a little cleaning and decided to connect it back up and on boost it hits a massive flat spot and dies but disconnected drives and boost fine.
Any ideas peeps??

 

What is controlling the boost when it is disconnected ?
I would suggest taking it easy for now and get your car booked in somewhere to get looked at.
tabetha

 

My gentle right foot!!!!
I intend to get it chipped so fingers crossed it'll get sorted at that point but like you mentioned i was a little concerned and curious!!!