Car was running fine apart from a flat spot most noticable in first and noisy DV. I have just replaced the DV with Forge 007 and also replaced the "totally severed" Crank case breather with a nice shiny black eurojet one - didnt replace the bottom one as I didn't have time (must get round to it soon though) car seems to pull just as well and no more blow off noises however the idle is intermitantly rough. IE idles at 750ish for ten seconds then drops to 550-600 and back up to 800 then settles again for 8-10 seconds? I can't belive that it ran smoother with a great big gapping hole in the breather system? like I said this is intermitant but more so than not. Hot or cold not mush difference either?

need to get it sorted as its supposed to be going in for gas conversion on the weekend.

Either find one of the vacuum pipes is split or the throttle body needs resetting

Hi Lummox. whats the easiest way to locate a vacuum leak? and is that where you turn ignition on and wait till throttle stops whining?

Throttle body alignment really needs to be carried out with VAG COM.

Easiest way to locate the air leak? Listen.

Move about the pipes under the inlet manifold and see if the engine note changes or you hear a leak.

just a "quick" update - the car was due for LPG install this weekend so I had to work quick to try and rectify the Idle problems. VAG COM cable from Ebay turned up Thursday so had a quick check of the codes

17608 - Boost Pressure Control Valve (N249): Mechanical Malfunction - Intermittent

17545 P1137 Long Term Fuel Trim Add.Fuel,Bank1 System too Rich - Intermittent

17705 P1297 Connection turbocharger - throttle valve pressure hose

wasn't sure if these were from before I replaced the DV and top hose so cleared them out and used for the day to see what came back, 17705 + 17545. so stripped the black plate off the inlet manifold to have a good look.( there was oil in the area around the pipe that goes through the manifold) The lower breather pipe had 2 splits and the small one (06a103221bk) that goes to the inlet manifold was like putty and had a huge split in it. already had the lower pipe but couldn't get the small pipe in time so used a length of silicone fuel line that I had spare. The lower breather pipe which had originally felt OK when I did the top hose just fell apart when I started working it loose. got it all back together OK but managed to crack my dip stick(common problem it would seem) took the car for a run and seems to pull stronger but still suffered from dip in first and intermitant Idle.

Today I pulled the MAF and the Idle was rock solid - Result. But I still think I have a boost leak which I need to get sorted when I get the car back. :(

NEW problem has shown up during all this but only on cold starting the engine, sounds like there is an exhaust leak (blowing) toward the front of the car. got out to investigate and in very little time there was a whoosh and then what sounded like a turbine slowing to a stop and the blowing went away? car ran fine after that...is there a valve that could be causing this if so which one?:confused:

The blowing noise just sounds like the normal operation of the secondary air injection maybe.

Leaking vacuum pipes then causing a 17705 fault, damn I hate being right

NEW problem has shown up during all this but only on cold starting the engine, sounds like there is an exhaust leak (blowing) toward the front of the car. got out to investigate and in very little time there was a whoosh and then what sounded like a turbine slowing to a stop and the blowing went away? car ran fine after that...is there a valve that could be causing this if so which one?:confused:

Sounds like the secondry air pump too me, which is perfectly normal

found this after a quick search Step-by-step guide for repairing the Secondary Air Pump (with pictures) - uk-mkivs and will have to give it a go when I get the car back..... cheers guys - your help has been invaluable..

do MAF's tend to clean up OK or are they best replaced? the guy doing the lpg conversion can change it if needed (he needs the car running 100% to make sure the conversion is at its best)

I don't think there is anything wrong with your secondary air pump tbh.

It is used to get the engine up to temperature quicker on cold starts. Yes it does sound a bit worrying but it normal. You should hear it for about 1 min after cold start and your revs will rise too about 1250 rpm.

You could try cleaning the maf but it may not work any better, I suppose it's worth ago though.