what does the pipe exactly do that goes from inlet manifold to the ecu ? as my mates running 15 psi and his isnt connected

 

Not sure, but I guess there's a MAP (manifold-absolute-pressure)-Sensor inside the ECU.

If you have the hose disconnected, the ECU won't be informed about boost pressure. I guess somebody tried to bypass overboost protection by doing this. Not good...

 

It wont know when the cars on boost so it wont run on boost fuel enrichment (afaik?) get it connected or you'll be building a new engine !!

 

VRRRRRRRRRRRRM BANG chug chug chuggggggggg!!!!!!

 

MAP SENSOR PIPE

 

Has nothing to do with fuelling, but with it disconnected it doesn't know to retard ignition advance and it doesn't know to control the Ĺmĺl-valve properly if connected. I run my car like this for some time back in the KE-jet days, but the distributor has to be turned to retard the basic advance setting a little bit.
As said there's a huge risk of breaking something if one doesn't know what he's doing.