manifold chatter on s4

[hondansxr]

i sometimes get a chattering from my manifold its a v8 2003 my i thought it was a tappet gone but when i put pressure on the rod from the vacuum unit to the manifold adjuster it stops ???? any help would be appreciated
i have seen on a usa forum of an ecu upgrade ??
when driving it seems to go flat when accelerating and that causes the diagnostic to throw misfire faults ?

 

[dualmono21]

your on about the intake manifold butterflies
these can sometimes stick open or not open above 5000rpm losing you around 60bhp

the way to check this is
remove the front top engine cover
just behind the front panel right in the middle of the engine you should see a black lever which has a spring on it
when this is working correctly it should actuate at 5000rpm and open the secondary butterflies to allow more air into the engine
if its isnt working or its sticking it can often cause problems and cel codes

warm the engine up and rev the engine past 5000rpm
the lever has two positions fully open or fully closed and shouldnt be anything in between
if it is and you can move the lever by hand and the noise stops you can try to take it apart and clean it with the aid of a very soft wire brush (be warned if you lose any parts or break anything you will need a new inlet manifold as the part isnt sold seperate)
i have seen nothing as regards an ecu upgrade im afraid