V6 missfire

[glen bongo]

hi everyone was out in the bongo today. it felt a bit slugish between 1800-2300 revs. on the way home it started to get a bit loud
and a lot more slugish stopped had a look underneath the pipe coming out the cat was glowing red let it cool for 20 mins hit the road
again felt a bit better for a wile. stopped and checked underneath a few times the last time pretty much all the cat and the flexi pipe were red
hot gave it a good wile to cool down the last 15 miles of the road are dual carigway and it drove much better got home checked underneath
straight away only the start of pipe after the cat was red. hot mate whos a mechanic came round he said it was definetly unburnt fuel going
in to the cat.he checked the plugs and the leads seamed to run better took it round the bloke it ran well as soonas we went on to bigger roads
and was accelerating a bit harder we could feel it missfire felxi pipe is totally done in probably the cat aswell
just after new year my heat warrning light came on it was quite slugish that day to changed the plugs and it seemed to sort the problem
since then ive had all the belts including pullys and tensioners and a full service done its ran pretty good all year once every now and again
if i stop at lights or a junction in D it runs a bit rough put it in to P or N and its fine this only happens two or three times a month i use the bongo
everyday
4 wees ago i finally found someone with the right lead for the diagnostics box it came up fault code1521 resistance felt at air intake manifold
VRIS solenoid valve in the manual
is it more an auto electricians job as in the manual it says to check voltage etc? guy who gave me the code thought the work i had done had sorted
had fixed the problem as the bongo was running perfectly at the time
thanks
jimmy

[mister munkey]

Any help?

http://www.igmaynard.co.uk/bongo/forum/ ... lit=lambda