Running problems - flat as a pancake!

[finite]

Hi all... this is an extract from my build thread just hoping someone can help!

On idle the engine hunts, when cold it's impossible to get idle unless the throttle stopper screw is wound in some way which means as it heats up the idle ends up being up at 1500 rpm.  Setting it back down to around 900rpm once hot the wide band reading is close to pure oxygen which i'm taking a guess is the result of the ICV playing up. Once hot it doesn't stall but still hunts for idle.

She feels gutless under 6k rpm, feels like overfueling. We've only tried the wideband on stationary idle and when stationary reving which shows a lambda of 12 so overfuelling looks likely.

I've done quite a few modifications and a lot of work on the car including:

TB heater plate removal as per guide on this forum
Heater matrix bypass
Cold air box and filter
Custom exhaust (standard manifold, downpipe modified to include oval silencer, rear section modified to include round silencer, stainless DTM can)

Here's the full build thread:
http://m42club.com/forums/showthread.php?t=7825&page=1

[Jimmy Lewis]

I would make sure all of the ignition system is in order first. I would check the coils and wires as well as clean the ICV just for kicks. My outright guess is that you are getting poor spark on a cylinder or none at all. That would explain the sluggishness as well as the rich O2 reading. Good luck.

[finite]

Hey Jim thanks for the response.  Haven't checked the spark yet, but have replaced plugs.  Leads look in good physical order (outside and in).  Car doesn't sound like it's missing or feel like it, does feel like overfueling though.

Done some more reading, going to replace ICV just ordered one, little suprised though as I did clean it out thoroughly with parts/tool cleaner.

As I've had the whole inlet system apart and back together I'm wondering if I may have a vacuum leak somewhere.  I've replaced lower inlet, upper inlet and TB gaskets with genuine BMW.  Always possible I didn't fit a manifold right. Done the TB heater plate removal mod.  Wonder if the silicone hose I've used between the ICV and the inlet manifold is holding up or is actually collapsing under vacuum, it's just the cheap stuff not reinforced as is the hose from the rocker cover to the TB.  

Then there's a million and one other possibilities!  

Nurburgring... 3 weeks.