ay guys

I have just replaced my master cylinder and brake booster, the booster was a recondition one (alot cheaper then brand new) and the MC is a brand spanker. After i finished the work and started the engine i could see the Brake fault light on the dash. Ive double checked all connections and they are fine. the engine is also running very rough, especially after i take my foot off the throttle when im coming to a stop, it completely loses its revs and shuts off. i think it could be a vacuum prob at the booster but am unsure. also the brake pedal is still very soft and i did bleed the system, so i thawt there was a leek but no leak was visible and there is no fluid loss. could it be that thers is a lot of air in the hydraulic system which is causing this prob with the fault light? soft pedal? and angine shutting down?

and its an EF Gli

I'd say you are right on the money. Youv'e done some major work to the barake system and there is bound to be a lot of air in the pipework, you are going to need to bleed a lot of fluid out to ensure all air is removed.