I've only had my car a short time and its already doing my head in trying to get parts and sort things out, its the boost again, I know where all the vac hoses go around the n75 and i took the nasty mbc out and it will only boost to 4psi, when i put the mbc back and plumb it before the n75 it will spike to 22 then go to around 16-18psi, it will the drop to 12 then go back up to 16-18 and hold. I can't see it being a boost leak as it will hold there for as long as i need to. and me being an idiot and buying a 2.5 means i have to get the valve from audi and wait a week as its a "back order from germany". if i take the mbc out and it only boosts at 4psi its flat (obviously) or if i put the mbc it it spikes and goes up and down, right...rant over any ideas please?????