Quote Originally Posted by JohnL View Post
As to running rich, don't know why, sounds like a seperate problem. Maybe try resetting the ECU?
Had a thought, try this; attached to the fuel rail there is a return valve that allows excess fuel pressure to bleed off back to the tank. It has a low pressure return fuel line at one end and a rubber vacuum tube at the other. This tube is attached to the plenum. This thing works is to keep fuel pressure at X psi above manifold pressure, whether this at any moment be at or below atmspheric (or in your case with turbo, above).

Inside this valve is a diaphram, if this diaphram leaks then pressurised fuel from the rail can leak into the plenum through the vacuum tube. The obvious result will be running rich, which may be worse at certain rpm than at other rpm.

I suppose it also could be that if this valve isn't working (but not leaking as described), that the fuel pressure might be too high, which could also cause rich running...?

Diagnosis? It might not be a good thing to block the vacuum tube, you might try it but I don't know what this will do (probably cause a too high pressure?). Try pulling the vacuum tube off and sniffing it for a petrol smell (it shouldn't smell of fuel), or maybe some fuel may even leak out?